Phosphate glasses with high refractive index and low density

ABSTRACT

Glass compositions include niobia (Nb 2 O 5 ), phosphorus oxide (P 2 O 5 ) and titania (TiO 2 ) as essential components and may optionally include calcium oxide (CaO), potassium oxide (K 2 O), barium oxide (BaO), sodium oxide (Na 2 O), lithium oxide (Li 2 O), magnesia (MgO), zinc oxide (ZnO) and other components. The glasses may be characterized by high refractive index at 587.56 nm at comparably low density at room temperature.

This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 63/140,419 filed on Jan. 22, 2021, the content of which is relied upon and incorporated herein by reference in its entirety.

FIELD

The present disclosure generally relates to phosphate glasses having a high refractive index and low density.

BACKGROUND

Glass is used in a variety of optical devices, examples of which include augmented reality devices, virtual reality devices, mixed reality devices, eye wear, etc. Desirable properties for this type of glass often include a high refractive index and a low density. Additional desirable properties may include high transmission in the visible and near-ultraviolet (near-UV) range of the electromagnetic spectrum and/or low optical dispersion. It can be challenging to find glasses having the desired combination of these properties and which can be formed from compositions having good glass-forming ability. For example, generally speaking, as the refractive index of a glass increases, the density also tends to increase. Species such as TiO₂ and Nb₂O₅ are often added to increase the refractive index of a glass without increasing the density of the glass. However, these materials often absorb blue and UV light, which can undesirably decrease the transmittance of light in this region of the spectrum by the glass. Often, attempts to increase the refractive index of a glass while maintaining a low density, and without decreasing transmittance in the blue and UV region of the spectrum, can result in a decrease in the glass-forming ability of the material. For example, crystallization and/or liquid-liquid phase separation can occur during cooling of the glass melt at cooling rates that are generally acceptable in the industry. Typically, the decrease in glass-forming ability appears as the amount of certain species, such as ZrO₂, Y₂O₃, Sc₂O₃, BeO, etc. increases.

Low density, high refractive index glasses often belong to one of two types of chemical systems, based on the glass formers used: (a) silicoborate or borosilicate glasses in which SiO₂ and/or B₂O₃ are used as the main glass formers and (b) phosphate glasses in which P₂O₅ is used as a main glass former. Glasses which rely on other oxides as main glass formers, such as GeO₂, TeO₂, Bi₂O₃, and V₂O₅, can be challenging to use due to cost, glass-forming ability, optical properties, and/or production requirements.

Phosphate glasses can be characterized by a high refractive index and low density, however, phosphate glasses can be challenging to produce due to volatilization of P₂O₅ from the melts and/or risks of platinum incompatibility. In addition, phosphate glasses are often highly colored and may require an extra bleaching step to provide a glass having the desired transmittance characteristic. Furthermore, phosphate glasses exhibiting a high refractive index also tend to have an increase in optical dispersion, which may be usable for some applications.

In view of these considerations, there is a need for phosphate glasses having a high refractive index and low density, optionally in combination with a high transmittance in the visible and near UV-range, and/or which are made from compositions that provide good glass-forming ability.

SUMMARY

According to an embodiment of the present disclosure, a glass comprising a plurality of components is disclosed, the glass has a composition of the components comprising greater than or equal to 10.0 mol. % and less than or equal to 40.0 mol. % P₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 40.0 mol. % TiO₂, greater than or equal to 0.5 mol. % and less than or equal to 35.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Al₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. % V₂O₅, greater than or equal to 0.5 mol. % and less than or equal to 35.0 mol. % for a sum of CaO+SrO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % for a sum of TeO₂+SnO₂+SnO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % for a sum of SiO₂+GeO₂ and may optionally contain one or more components selected greater than or equal to BaO, Na₂O, Li₂O, WO₃, Bi₂O₃, B₂O₃, ZnO, ZrO₂, PbO, Tl₂O, Ag₂O, CdO, Cs₂O, Ga₂O₃, La₂O₃, MoO₃ and Ta₂O₅, the glass satisfying the condition: P_(n)−(1.83+0.04*P_(d))>0.00, where P_(n) is a refractive index parameter, calculated greater than or equal to the glass composition in terms of mol. % of the components according to the Formula (I): P _(n)=−0.0043794*P₂O₅+0.0072428*Nb₂O₅+0.0037304*TiO₂−0.00039553*BaO−0.0032012*K₂O−0.00060689*CaO−0.0024218*Na₂O−0.0014988*Li₂O+0.0028587*WO₃+0.0083295*Bi₂O₃−0.0031637*B₂O₃−0.0030702*SiO₂−0.00030248*ZnO+0.0020025*ZrO₂−0.0018173*MgO−0.0032886*Al₂O₃+0.0024221*TeO₂+0.0038137*PbO−0.0016392*GeO₂+0.0063024*Tl₂O+0.0048765*Ag₂O+1.81451,  (I)

P_(d) is a density parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (II): P _(d)[g/cm³]=3.98457−0.015773*Al₂O₃−0.014501*B₂O₃+0.019328*BaO+0.060758*Bi₂O₃−0.0012685*CaO+0.023111*CdO+0.0053184*Cs₂O+0.011488*Ga₂O₃−0.0015416*GeO₂−0.013342*K₂O+0.058319*La₂O₃−0.007918*Li₂O−0.0021423*MgO−0.0024413*MoO₃−0.0082226*Na₂O+0.0084961*Nb₂O₅−0.020501*P₂O₅+0.038898*PbO−0.012720*SiO₂+0.013948*SrO+0.047924*Ta₂O₅+0.011248*TeO₂−0.0092491*V₂O₅+0.028913*WO₃+0.0074702*ZnO+0.0096721*ZrO₂,  (II) where a symbol “*” means multiplication.

According to another embodiment of the present disclosure, a glass comprising a plurality of components is disclosed, the glass has a composition of the components comprising greater than or equal to 17.0 mol. % and less than or equal to 27.0 mol. % P₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 40.0 mol. % TiO₂, greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Al₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. % V₂O₅, greater than or equal to 0.0 mol. % Li₂O, greater than or equal to 5.0 mol. % RO, greater than or equal to 5.0 mol. % Alk₂O, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % for a sum of SiO₂+GeO₂, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % for a sum of TeO₂+SnO₂+SnO and may optionally contain one or more components selected greater than or equal to BaO, Na₂O, WO₃, B₂O₃, ZnO, ZrO₂, PbO, CdO, Cs₂O, SrO, Tl₂O, Ag₂O, Ga₂O₃, La₂O₃, MoO₃ and Ta₂O₅, the glass satisfying the condition: P_(n)−(1.83+0.04*P_(d))−(−0.06+0.0013*(TiO₂+Nb₂O₅))>0.00, where P_(n) is a refractive index parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (I): P _(n)=−0.0043794*P₂O₅+0.0072428*Nb₂O₅+0.0037304*TiO₂−0.00039553*BaO−0.0032012*K₂O−0.00060689*CaO−0.0024218*Na₂O−0.0014988*Li₂O+0.0028587*WO₃+0.0083295*Bi₂O₃−0.0031637*B₂O₃−0.0030702*SiO₂−0.00030248*ZnO+0.0020025*ZrO₂−0.0018173*MgO−0.0032886*Al₂O₃+0.0024221*TeO₂+0.0038137*PbO−0.0016392*GeO₂+0.0063024*Tl₂O+0.0048765*Ag₂O+1.81451,  (I) P_(d) is a density parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (II): P _(d)[g/cm³]=3.98457−0.015773*Al₂O₃−0.014501*B₂O₃+0.019328*BaO+0.060758*Bi₂O₃−0.0012685*CaO+0.023111*CdO+0.0053184*Cs₂O+0.011488*Ga₂O₃−0.0015416*GeO₂−0.013342*K₂O+0.058319*La₂O₃−0.007918*Li₂O−0.0021423*MgO−0.0024413*MoO₃−0.0082226*Na₂O+0.0084961*Nb₂O₅−0.020501*P₂O₅+0.038898*PbO−0.012720*SiO₂+0.013948*SrO+0.047924*Ta₂O₅+0.011248*TeO₂−0.0092491*V₂O₅+0.028913*WO₃+0.0074702*ZnO+0.0096721*ZrO₂,  (II) where RO is a total sum of divalent metal oxides, Alk₂O is a total sum of alkali metal oxides and a symbol “*” means multiplication.

These and other aspects, objects, and features of the present disclosure will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot illustrating the relationship between the refractive index n_(d) and the refractive index parameter P_(n) calculated by formula (I) for some Comparative Glasses and some Exemplary Glasses according to an embodiment of the present disclosure.

FIG. 2 is a plot illustrating the relationship between the density at room temperature d_(RT) and the density parameter P_(d) calculated by formula (II) for some Comparative Glasses and some Exemplary Glasses according to an embodiment of the present disclosure.

FIG. 3 is a plot of a composition dependence of the thermal expansion coefficient for some comparative glasses.

FIG. 4 is a plot illustrating the relationship between the density parameter P_(d) and the refractive index parameter P_(n) for some Comparative Glasses and some Exemplary Glasses according to an embodiment of the present disclosure.

FIG. 5 is a plot illustrating the relationship between the density at room temperature d_(RT) and the refractive index n_(d) for some Comparative Glasses and some Exemplary Glasses according to an embodiment of the present disclosure.

FIG. 6 is a plot illustrating the relationship between a sum of TiO₂+Nb₂O₅ and P_(n)−(1.83+0.04*P_(d)) for some Comparative Glasses and some Exemplary Glasses according to an embodiment of the present disclosure.

FIG. 7 is a plot illustrating the relationship between the a sum of TiO₂+Nb₂O₅ and n_(d)−(1.83+0.04*d_(RT)) for some Comparative Glasses and some Exemplary Glasses according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of various principles of the present disclosure. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present disclosure may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of various principles of the present disclosure. Finally, wherever applicable, like reference numerals refer to like elements.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including, without limitation, matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

Modifications of the disclosure will occur to those skilled in the art and to those who make or use the disclosure. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the disclosure, which is defined by the following claims, as interpreted according to the principles of patent law, including the doctrine of equivalents.

As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those skilled in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point.

The term “formed from” can mean one or more of comprises, consists essentially of, or consists of. For example, a component that is formed from a particular material can comprise the particular material, consist essentially of the particular material, or consist of the particular material.

The terms “free” and “substantially free” are used interchangeably herein to refer to an amount and/or an absence of a particular component in a glass composition that is not intentionally added to the glass composition. It is understood that the glass composition may contain traces of a particular constituent component as a contaminant or a tramp in an amount of less than 0.10 mol %.

As used herein, the term “tramp”, when used to describe a particular constituent component in a glass composition, refers to a constituent component that is not intentionally added to the glass composition and is present in an amount of less than 0.05 mol %. Tramp components may be unintentionally added to the glass composition as an impurity in another constituent component and/or through migration of the tramp component into the composition during processing of the glass composition.

The term “glass former” is used herein to refer to a component that, being solely present in the glass composition (i.e., without other components, except for tramps), is able to form a glass when cooling the melt at a rate of not greater than about 200° C./min to about 300° C./min.

The term “modifier”, as used herein, refers to the oxides of monovalent or divalent metals, i.e., R₂O or RO, where “R” stands for a cation. Modifiers can be added to a glass composition to change the atomic structure of the melt and the resulting glass. In some embodiments, the modifier may change the coordination numbers of cations present in the glass formers (e.g., boron in B₂O₃), which may result in forming a more polymerized atomic network and, as a result, may provide better glass formation.

As used herein, the term “RO” refers to a total content of divalent metal oxides, the term “R₂O” refers to a total content of monovalent metal oxides, and the term “Alk₂O” refers to a total content of alkali metal oxides. The term R₂O encompasses alkali metal oxides (Alk₂O), in addition to other monovalent metal oxides, such as Ag₂O, Tl₂O, and Hg₂O, for example. As discussed below, in the present disclosure, a rare earth metal oxide is referred to herein by its normalized formula (RE₂O₃) in which the rare earth metal has the redox state “+3,” and thus rare earth metal oxides are not encompassed by the term RO.

As used herein, the term “rare earth metals” refers to the metals listed in the Lanthanide Series of the IUPAC Periodic Table, plus yttrium and scandium. As used herein, the term “rare earth metal oxides,” is used to refer to the oxides of rare earth metals in different redox states, such as “+3” for lanthanum in La₂O₃, “+4” for cerium in CeO₂, “+2” for europium in EuO, etc. In general, the redox states of rare earth metals in oxide glasses may vary and, in particular, the redox state may change during melting, based on the batch composition and/or the redox conditions in the furnace where the glass is melted and/or heat-treated (e.g., annealed). Unless otherwise specified, a rare earth metal oxide is referred to herein by its normalized formula in which the rare earth metal has the redox state “+3.” Accordingly, in the case in which a rare earth metal having a redox state other than “+3” is added to the glass composition batch, the glass compositions are recalculated by adding or removing some oxygen to maintain the stoichiometry. For example, when CeO₂ (with cerium in redox state “+4”) is used as a batch component, the resulting glass composition is recalculated assuming that two moles of CeO₂ is equivalent to one mole of Ce₂O₃, and the resulting glass composition is presented in terms of Ce₂O₃. As used herein, the term “RE_(m)O_(n)” is used to refer to the total content of rare earth metal oxides in all redox states present, and the term “RE₂O₃” is used to refer to the total content of rare earth metal oxides in the “+3” redox state.

The measured density values for the glasses reported herein were measured at room temperature in units of g/cm³ by Archimedes method in water with an error of 0.001 g/cm³. As used herein, density measurements at room temperature (specified as d_(RT) and expressed herein in units of g/cm³) are indicated as being measured at 20° C. or 25° C., and encompass measurements obtained at temperatures that may range from 20° C. to 25° C. It is understood that room temperature may vary between about 20° C. to about 25° C., however, for the purposes of the present disclosure, the variation in density within the temperature range of 20° C. to 25° C. is expected to be less than the error of 0.001 g/cm³, and thus is not expected to impact the room temperature density measurements reported herein.

As used herein, good glass-forming ability refers to a resistance of the melt to devitrification as the material cools. Glass-forming ability can be measured by determining the critical cooling rate of the melt. The terms “critical cooling rate” or “v_(cr)” are used herein to refer to the minimum cooling rate at which a melt of a given composition forms a glass free of crystals visible under an optical microscope under magnification from 100× to 500×. The critical cooling rate can be used to measure the glass-forming ability of a composition, i.e., the ability of the melt of a given glass composition to form glass when cooling. Generally speaking, the lower the critical cooling rate, the better the glass-forming ability.

The term “liquidus temperature” (denoted “T_(liq)”) is used herein to refer to a temperature above which the glass composition is completely liquid with no crystallization of constituent components of the glass. The liquidus temperature values reported herein were obtained by measuring samples using one of the following three tests: (1) DSC (differential scanning calorimetry), (2) isothermal hold of samples wrapped in platinum foil, or (3) gradient boat liquidus method. The tests were crosschecked and similar results were obtained for each of the tests. For samples measured using DSC, powdered samples were heated at 10 K/min to 1250° C. The end of the endothermal event corresponding to the melting of crystals was taken as the liquidus temperature. For samples measured using the isothermal hold method, a glass block (about 1 cm³) was wrapped in platinum foil, to avoid volatilization, placed in a furnace at a given temperature for 17 hours, then quickly removed from the furnace and cooled in air. The glass block was then observed under an optical microscope to check for crystals in the bulk of the sample. Sparse surface crystals were ignored if they appeared after holding at the temperature that did not exceed the observed liquidus temperature as described above for more than 30-40° C.; otherwise, the test was repeated. For samples measured using the gradient boat liquidus method, the procedure described in the standard ASTM C829-81 was followed. This involves placing crushed glass particles in a platinum boat, placing the boat in a furnace having a region of gradient temperatures, heating the boat in an appropriate temperature region for 24 hours, and determining by means of microscopic examination the highest temperature at which crystals appear in the interior of the glass. More particularly, the glass sample is removed from the Pt boat in one piece, and examined using polarized light microscopy to identify the location and nature of crystals which have formed against the Pt and air interfaces, and in the interior of the sample. Because the gradient of the furnace is very well known, temperature vs. location can be well estimated, within 5-10° C. The temperature at which crystals are observed in the internal portion of the sample is taken to represent the liquidus of the glass (for the corresponding test period). Testing is sometimes carried out at longer times (e.g. 72 hours), to observe slower growing phases. The liquidus viscosity in poises was determined from the liquidus temperature and the coefficients of the Fulcher equation.

The refractive index values reported herein were measured at room temperature (about 25° C.), unless otherwise specified. The refractive index values for a glass sample were measured using a Metricon Model 2010 prism coupler refractometer with an error of about ±0.0002. Using the Metricon, the refractive index of a glass sample was measured at two or more wavelengths of about 406 nm, 473 nm, 532 nm, 633 nm, 828 nm, and 1064 nm. The measured dependence characterizes the dispersion and was then fitted with a Cauchy's law equation or Sellmeier equation to allow for calculation of the refractive index of the sample at a given wavelength of interest between the measured wavelengths. The term “refractive index n_(d)” is used herein to refer to a refractive index calculated as described above at a wavelength of 587.56 nm, which corresponds to the helium d-line wavelength. The term “refractive index n_(C)” is used herein to refer to a refractive index calculated as described above at a wavelength of 656.3 nm. The term “refractive index n_(F)” is used herein to refer to a refractive index calculated as described above at a wavelength of 486.1 nm. The term “refractive index n_(g)” is used herein to refer to a refractive index calculated as described above at a wavelength of 435.8 nm.

As used herein, the terms “high refractive index” or “high index” refers to a refractive index value n_(d) of a glass that is greater than or equal to at least 1.80, unless otherwise indicated. Where indicated, the terms “high refractive index” or “high index” refer to a refractive index value of a glass that is greater than or equal to at least 1.85, or greater than or equal to 1.90, or greater than or equal to 1.95, or greater than or equal to 2.00.

The terms “dispersion” and “optical dispersion” are used interchangeably to refer to a difference or ratio of the refractive indices of a glass sample at predetermined wavelengths. One numerical measure of optical dispersion reported herein is the Abbe number, which can be calculated by the formula: ν_(x)=(n_(x)−1)/(n_(F)−n_(C)), where “x” in the present disclosure stands for one of the commonly used wavelengths (for example, 587.56 nm [d-line] for ν_(d) or 589.3 nm [D-line] for V_(D)), n_(x) is the refractive index at this wavelength (for example, n_(d) for ν_(d) and n_(D) for V_(D)), and n_(F) and n_(C) are refractive indices at the wavelengths 486.1 nm (F-line) and 656.3 nm (C-line), respectively. The numerical values of ν_(d) and ν_(D) differ very slightly, mostly within ±0.1% to ±0.2%. As reported herein, the dispersion of a glass sample is represented by the Abbe number (ν_(d)), which characterizes the relationship between the refractive indices of the sample at three different wavelengths according to the following formula: ν_(d)=(n_(d)−1)/(n_(F)−n_(C)), where n_(d) is the calculated refractive index at 587.56 nm (d-line), n_(F) is the calculated refractive index at 486.1 nm (F-line), and n_(C) is the calculated refractive index at 656.3 nm (C-line). A higher Abbe number corresponds to a lower optical dispersion.

The numerical value for an Abbe number corresponding to “high dispersion” or “low dispersion” may vary depending on the refractive indices for which the Abbe number is calculated. In some cases, an Abbe number corresponding to “low dispersion” for a high refractive index glass may be lower than an Abbe number corresponding to “low dispersion” for a low refractive index glass. In other words, as the calculated refractive index value increases, the value of the Abbe number corresponding to low dispersion decreases. The same relates to “high dispersion” as well.

The term “α,” or “α₂₀₋₃₀₀,” as used herein, refers to the coefficient of linear thermal expansion (CTE) of the glass composition over a temperature range from 20° C. (room temperature, or RT) to 300° C. This property is measured by using a horizontal dilatometer (push-rod dilatometer) in accordance with ASTM E228-11. The numeric measure of a is linear average value in a specified temperature range (e.g., RT to 300° C.) expressed as α=ΔL/(L₀ΔT), where L₀ is the linear size of a sample at some temperature within or near the measured range, and L is the change in the linear size (ΔL) in the measured temperature range ΔT.

The Young's elastic modulus E and the Poisson's ratio μ are measured by using Resonant Ultrasound Spectroscopy, using a Quasar RUSpec 4000 available from ITW Indiana Private Limited, Magnaflux Division.

The glass transition temperature (T_(g)) is measured by differential scanning calorimeter (DSC) at the heating rate of 10 K/min after cooling in air.

The term “annealing point,” as used herein, refers to the temperature determined according to ASTM C598-93(2013), at which the viscosity of a glass of a given glass composition is approximately 1013.2 poise.

The symbol “*” means multiplication when used in any formula herein.

Glass composition may include phosphorus oxide (P₂O₅). The glass compositions in the embodiments described herein comprise phosphorus oxide (P₂O₅) as a main glassformer. Greater amounts of P₂O₅ increases the melt viscosity at a given temperatures, which inhibits crystallization from the melt when cooling and, therefore, improves the glass-forming ability of the melt (i.e. lowers the critical cooling rate of the melt). However, P₂O₅, being added to a glass composition, significantly decreases the refractive index, which makes it more difficult to reach the high index. Accordingly, the content of P₂O₅ in high-index glasses is limited. In embodiments, the glass may contain phosphorus oxide (P₂O₅) in an amount from greater than or equal to 10.0 mol. % to less than or equal to 40.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain P₂O₅ in an amount greater than or equal to 10.0 mol. %, greater than or equal to 11.0 mol. %, greater than or equal to 12.0 mol. %, greater than or equal to 13.0 mol. %, greater than or equal to 15.0 mol. %, greater than or equal to 17.0 mol. %, greater than or equal to 20.0 mol. %, greater than or equal to 20.4 mol. %, greater than or equal to 21.0 mol. %, greater than or equal to 23.0 mol. %, greater than or equal to 25.0 mol. %, greater than or equal to 30.0 mol. %, greater than or equal to 35.0 mol. %, greater than or equal to 37.0 mol. %, greater than or equal to 38.0 mol. %, or greater than or equal to 39.0 mol. %. In some other embodiments, the glass composition may contain P₂O₅ in an amount less than or equal to 40.0 mol. %, less than or equal to 39.0 mol. %, less than or equal to 38.0 mol. %, less than or equal to 37.0 mol. %, less than or equal to 35.0 mol. %, less than or equal to 30.0 mol. %, less than or equal to 27.0 mol. %, less than or equal to 25.0 mol. %, less than or equal to 24.8 mol. %, less than or equal to 24.5 mol. %, less than or equal to 20.0 mol. %, less than or equal to 15.0 mol. %, less than or equal to 13.0 mol. %, less than or equal to 12.0 mol. %, or less than or equal to 11.0 mol. %. In some more embodiments, the glass composition may contain P₂O₅ in an amount greater than or equal to 10.0 mol. % and less than or equal to 40.0 mol. %, greater than or equal to 17.0 mol. % and less than or equal to 27.0 mol. %, greater than or equal to 20.0 mol. % and less than or equal to 25.0 mol. %, greater than or equal to 20.4 mol. % and less than or equal to 24.8 mol. %, greater than or equal to 21.0 mol. % and less than or equal to 24.5 mol. %, greater than or equal to 22.81 mol. % and less than or equal to 24.99 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 11.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 11.0 mol. % and less than or equal to 24.8 mol. %, greater than or equal to 11.0 mol. % and less than or equal to 13.0 mol. %, greater than or equal to 12.0 mol. % and less than or equal to 40.0 mol. %, greater than or equal to 12.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 12.0 mol. % and less than or equal to 13.0 mol. %, greater than or equal to 13.0 mol. % and less than or equal to 40.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 40.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 27.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 24.5 mol. %, greater than or equal to 20.0 mol. % and less than or equal to 37.0 mol. %, greater than or equal to 20.0 mol. % and less than or equal to 24.5 mol. %, greater than or equal to 24.5 mol. % and less than or equal to 37.0 mol. %, greater than or equal to 24.5 mol. % and less than or equal to 27.0 mol. %, greater than or equal to 24.8 mol. % and less than or equal to 40.0 mol. %, greater than or equal to 24.8 mol. % and less than or equal to 38.0 mol. %, greater than or equal to 25.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 25.0 mol. % and less than or equal to 27.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 22.0 mol. %, greater than or equal to 25.0 mol. % and less than or equal to 35.0 mol. %, or greater than or equal to 16.0 mol. % and less than or equal to 28.0 mol. %.

Glass composition may include divalent metal oxides (RO). Divalent metal oxides, such as alkaline earth metal oxides (BeO, MgO, CaO, SrO and BaO), zinc oxide (ZnO), cadmium oxide (CdO), lead oxide (PbO) and others, being added to a glass, provide comparably high refractive indexes, greater than those for most of monovalent oxides. Some divalent metal oxides, such as, for example, CaO, SrO and ZnO, also provide comparably low density, therefore, increasing the ratio of the refractive index to density and, accordingly, improving the performance of optical glasses in certain applications. In addition, divalent metal oxides may help to increase the solubility of the high index components, such as TiO₂, Nb₂O₅ and WO₃, which indirectly leads to a further increase in the refractive index at a comparable density. Also, some divalent metal oxides, such as, for example, ZnO and MgO, provide comparably low thermal expansion coefficient, which reduces the thermal stresses formed in the glass articles when cooling and, therefore, to improve the quality of the glass articles. However, at high amounts, divalent metal oxides may cause crystallization of refractory minerals from the melts or liquid-liquid phase separation, which may reduce the glass-forming ability of glasses. Also, some divalent metal oxides, such as, for example, PbO and CdO, may raise environmental concerns. Accordingly, the amount of divalent metal oxides in glass compositions of the present disclosure is limited.

In some embodiments, the glass composition may contain divalent metal oxides (RO) in an amount greater than or equal to 0.0 mol. %, or greater than or equal to 5.0 mol. %.

Glass composition may include calcium oxide (CaO). Calcium oxide provides the highest ratio of the refractive index to density of glasses among the known monovalent and divalent metal oxides. Also, in some embodiments, CaO may help to increase the solubility of Nb₂O₅ and TiO₂, which contributes to an increase in refractive index at comparably low density. However, if the amount of CaO in a glass is too high, it may cause crystallization of refractory species, such as calcium titanates (CaTiO₃, CaTi₂O₅, etc.) calcium niobate (CaNb₂O₆), calcium metasilicate (CaSiO₃) and others, which may reduce the viscosity at the liquidus temperature and, therefore, increase the critical cooling rate, which may cause crystallization of the glass-forming melt when cooling. That is why the amount of CaO in glasses of the present disclosure is limited. In embodiments, the glass may contain calcium oxide (CaO) in an amount greater than or equal to greater than or equal to 0.0 mol. % to less than or equal to 35.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain CaO in an amount greater than or equal to 0.0 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 3.0 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 10.0 mol. %, greater than or equal to 15.0 mol. %, greater than or equal to 20.0 mol. %, greater than or equal to 25.0 mol. %, greater than or equal to 30.0 mol. %, greater than or equal to 32.0 mol. %, greater than or equal to 33.0 mol. %, or greater than or equal to 34.0 mol. %. In some other embodiments, the glass composition may contain CaO in an amount less than or equal to 35.0 mol. %, less than or equal to 34.0 mol. %, less than or equal to 33.0 mol. %, less than or equal to 32.0 mol. %, less than or equal to 30.0 mol. %, less than or equal to 25.0 mol. %, less than or equal to 20.0 mol. %, less than or equal to 17.0 mol. %, less than or equal to 15.5 mol. %, less than or equal to 15.0 mol. %, less than or equal to 10.0 mol. %, less than or equal to 5.0 mol. %, less than or equal to 3.0 mol. %, less than or equal to 2.0 mol. %, or less than or equal to 1.0 mol. %. In some more embodiments, the glass composition may contain CaO in an amount greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 17.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 15.5 mol. %, greater than or equal to 2.81 mol. % and less than or equal to 14.63 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 25.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 15.5 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 15.5 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 32.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 15.5 mol. % and less than or equal to 33.0 mol. %, greater than or equal to 15.5 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 15.5 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 7.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 20.0 mol. %, or greater than or equal to 5.0 mol. % and less than or equal to 26.0 mol. %.

Glass composition may include strontium oxide (SrO). In high-index phosphate glasses, SrO, like CaO, may improve the solubility of high index components. However, the solubility improvement is typically less for SrO than for CaO. Also, SrO provides a somewhat greater density at comparable refractive indices than CaO. Accordingly, the amount of SrO in glasses of the present disclosure is limited, or glasses may be substantially free of SrO. In embodiments, the glass may contain strontium oxide (SrO) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 35.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain SrO in an amount greater than or equal to 0.0 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 3.0 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 10.0 mol. %, greater than or equal to 15.0 mol. %, greater than or equal to 20.0 mol. %, greater than or equal to 25.0 mol. %, greater than or equal to 30.0 mol. %, greater than or equal to 32.0 mol. %, greater than or equal to 33.0 mol. %, or greater than or equal to 34.0 mol. %. In some other embodiments, the glass composition may contain SrO in an amount less than or equal to 35.0 mol. %, less than or equal to 34.0 mol. %, less than or equal to 33.0 mol. %, less than or equal to 32.0 mol. %, less than or equal to 30.0 mol. %, less than or equal to 25.0 mol. %, less than or equal to 20.0 mol. %, less than or equal to 15.0 mol. %, less than or equal to 10.0 mol. %, less than or equal to 5.0 mol. %, less than or equal to 3.0 mol. %, less than or equal to 2.7 mol. %, less than or equal to 2.4 mol. %, less than or equal to 2.0 mol. %, or less than or equal to 1.0 mol. %. In some more embodiments, the glass composition may contain SrO in an amount greater than or equal to 0.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 2.7 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 2.4 mol. %, greater than or equal to 0.03 mol. % and less than or equal to 2.11 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 25.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 2.4 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 2.4 mol. %, greater than or equal to 2.4 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 2.7 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 2.7 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 2.7 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 32.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 32.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 14.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 28.0 mol. %, or greater than or equal to 8.0 mol. % and less than or equal to 28.0 mol. %.

Glass composition may include barium oxide (BaO). Barium oxide may increase the solubility of high index components, such as TiO₂ and Nb₂O₅, more than other divalent metal oxides, which may indirectly lead to a further increase in the refractive index at comparably low density. However, barium is a heavy element and, if added in a high amount, may increase the density of glass. Also, at high concentration, it may cause crystallization of such minerals as barium titanate (BaTiO₃), barium niobate (BaNb₂O₆), barium orthophosphate (Ba₃P₂O₈) and others, which may cause crystallization of a glass-forming melt when cooling. Accordingly, the amount of BaO in glasses of the present disclosure is limited, or glasses may be substantially free of BaO. In embodiments, the glass may contain barium oxide (BaO) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 20.1 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain BaO in an amount greater than or equal to 0.0 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.5 mol. %, greater than or equal to 4.5 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 10.0 mol. %, or greater than or equal to 15.0 mol. %. In some other embodiments, the glass composition may contain BaO in an amount less than or equal to 20.1 mol. %, less than or equal to 15.0 mol. %, less than or equal to 13.5 mol. %, less than or equal to 12.3 mol. %, less than or equal to 12.0 mol. %, less than or equal to 10.0 mol. %, or less than or equal to 5.0 mol. %. In some more embodiments, the glass composition may contain BaO in an amount greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 13.5 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 4.49 mol. % and less than or equal to 12.27 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 13.5 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 13.5 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 13.5 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 12.3 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 12.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 12.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 12.0 mol. % and less than or equal to 13.5 mol. %, greater than or equal to 12.0 mol. % and less than or equal to 12.3 mol. %, greater than or equal to 12.3 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 12.3 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 12.3 mol. % and less than or equal to 13.5 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 11.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 13.0 mol. %, or greater than or equal to 4.0 mol. % and less than or equal to 10.0 mol. %.

Glass composition may include magnesia (MgO). Magnesia is not frequently used in the high-index optical glasses. Magnesia reduces the low thermal expansion coefficient, which may be useful for reduction of thermal stresses formed in the glass articles when cooling them. However, magnesia provides a lower refractive index and a lower increase in the solubility of high index components than other divalent metal oxides, such as, for example, BaO, SrO, CaO and ZnO. Also, in phosphate glasses, adding MgO may cause crystallization of magnesium phosphate Mg₃P₂O₈, which may reduce the glass-forming ability of glasses. Accordingly, the amount of MgO in glass compositions of the present disclosure is limited, or glasses may be substantially free of MgO. In embodiments, the glass may contain magnesia (MgO) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 15.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain MgO in an amount greater than or equal to 0.0 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 3.0 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 10.0 mol. %, greater than or equal to 12.0 mol. %, greater than or equal to 13.0 mol. %, or greater than or equal to 14.0 mol. %. In some other embodiments, the glass composition may contain MgO in an amount less than or equal to 15.0 mol. %, less than or equal to 14.0 mol. %, less than or equal to 13.0 mol. %, less than or equal to 12.0 mol. %, less than or equal to 10.0 mol. %, less than or equal to 7.5 mol. %, less than or equal to 6.25 mol. %, less than or equal to 5.5 mol. %, less than or equal to 5.0 mol. %, less than or equal to 3.0 mol. %, less than or equal to 2.0 mol. %, or less than or equal to 1.0 mol. %. In some more embodiments, the glass composition may contain MgO in an amount greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 6.25 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 5.5 mol. %, greater than or equal to 0.52 mol. % and less than or equal to 4.73 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 6.25 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 6.25 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 13.0 mol. %, greater than or equal to 5.5 mol. % and less than or equal to 13.0 mol. %, greater than or equal to 5.5 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 5.5 mol. % and less than or equal to 6.25 mol. %, greater than or equal to 2.9 mol. % and less than or equal to 8.1 mol. %, greater than or equal to 8.9 mol. % and less than or equal to 14.2 mol. %, or greater than or equal to 2.1 mol. % and less than or equal to 8.0 mol. %.

Glass composition may include zinc oxide (ZnO). Zinc oxide provides a comparatively good refractive index to density ratio and may sometimes increase the solubility of titania, which indirectly increases the refractive index of glasses. However, it was found that in some embodiments, at high concentrations of ZnO, the glass-forming ability of the melt decreases and the melt may tend to crystallize during cooling. That is why the amount of ZnO in the glasses of the present disclosure is limited, or glass compositions may be free of ZnO. In embodiments, the glass may contain zinc oxide (ZnO) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 10.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain ZnO in an amount greater than or equal to 0.0 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.5 mol. %, greater than or equal to 5.0 mol. %, or greater than or equal to 7.5 mol. %. In some other embodiments, the glass composition may contain ZnO in amount less than or equal to 10.0 mol. %, less than or equal to 7.5 mol. %, less than or equal to 5.0 mol. %, less than or equal to 4.6 mol. %, less than or equal to 4.0 mol. %, or less than or equal to 2.5 mol. %. In some more embodiments, the glass composition may contain ZnO in an amount greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 4.6 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 1.4 mol. % and less than or equal to 3.66 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 4.6 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 4.6 mol. %, greater than or equal to 4.6 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 4.6 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 4.6 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 8.5 mol. %, greater than or equal to 6.8 mol. % and less than or equal to 9.6 mol. %, or greater than or equal to 3.3 mol. % and less than or equal to 6.0 mol. %.

Glass composition may include alkali metal oxides (Alk₂O). Alkali metal oxides (Li₂O, Na₂O, K₂O, Rb₂O and Cs₂O) may help to improve the solubility of high index components, such as TiO₂, Nb₂O₅ or WO₃, in the glass structure, which may lead to an increase in the refractive index at an acceptably low density. Most commonly, Li₂O, Na₂O and/or K₂O are used for this purpose. Among these three oxides, typically, K₂O provides the greatest effect on solubility of the high index components; however, addition of K₂O itself may reduce the refractive index, which reduces the mentioned effect. In contrast, Li₂O typically provides the greatest ratio of the refractive index to density among these three oxides, but has the lowest effect on solubility of the high index components. Sodium oxide (Na₂O) typically generates intermediate effects between Li₂O and K₂O. However, exact effects of these oxides on the glass-forming ability are difficult to predict, and in different embodiments, the desirable proportions between these oxides may be different. In particular, in some embodiments, it is desirable to add all of three oxides (Li₂O, Na₂O and K₂O), or two of them, together with each other. Also, in some embodiments, use of monovalent metal oxides (R₂O) together with divalent metal oxides (RO) improves the glass-forming ability of glasses and allows reaching higher refractive indices at comparable densities.

In some embodiments, the glass composition may contain alkali metal oxides in an amount greater than or equal to 0.0 mol. %, or greater than or equal to 5.0 mol. %.

Glass composition may include potassium oxide (K₂O). Potassium oxide may increase the solubility of high index components, such as TiO₂ and Nb₂O₅, more than other monovalent and divalent metal oxides, which may indirectly increase the refractive index at comparably low density. However, potassium oxide itself provides the lowest refractive index among the mentioned oxides. Therefore, at high concentrations of K₂O, it may be difficult to reach high refractive index. Accordingly, the amount of K₂O in glasses of the present disclosure is limited, or glasses may be substantially free of K₂O. In embodiments, the glass may contain potassium oxide (K₂O) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 35.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain K₂O in an amount greater than or equal to 0.0 mol. %, greater than or equal to 0.5 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 3.0 mol. %, greater than or equal to 3.5 mol. %, greater than or equal to 4.0 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 10.0 mol. %, greater than or equal to 15.0 mol. %, greater than or equal to 20.0 mol. %, greater than or equal to 25.0 mol. %, greater than or equal to 30.0 mol. %, greater than or equal to 32.0 mol. %, greater than or equal to 33.0 mol. %, or greater than or equal to 34.0 mol. %. In some other embodiments, the glass composition may contain K₂O in an amount less than or equal to 35.0 mol. %, less than or equal to 34.0 mol. %, less than or equal to 33.0 mol. %, less than or equal to 32.0 mol. %, less than or equal to 30.0 mol. %, less than or equal to 25.0 mol. %, less than or equal to 20.0 mol. %, less than or equal to 18.0 mol. %, less than or equal to 16.0 mol. %, less than or equal to 15.0 mol. %, less than or equal to 10.0 mol. %, less than or equal to 5.0 mol. %, less than or equal to 3.0 mol. %, less than or equal to 2.0 mol. %, or less than or equal to 1.0 mol. %. In some more embodiments, the glass composition may contain K₂O in an amount greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 18.0 mol. %, greater than or equal to 3.5 mol. % and less than or equal to 16.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 9.98 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 25.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 16.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 32.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 18.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 18.0 mol. % and less than or equal to 33.0 mol. %, greater than or equal to 18.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 18.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 14.0 mol. % and less than or equal to 25.0 mol. %, greater than or equal to 14.0 mol. % and less than or equal to 32.0 mol. %, or greater than or equal to 13.0 mol. % and less than or equal to 29.0 mol. %.

Glass composition may include sodium oxide (Na₂O). In high-index glasses, Na₂O acts like K₂O, improving the solubility of high index components, such as TiO₂, Nb₂O₅, WO₃ and others, but, at the same time, decreasing the refractive index of glasses. In most cases, the effect of Na₂O on solubility of high index components was found to be slightly lower than the corresponding effect of K₂O. However, Na₂O provides a lower thermal expansion coefficient than K₂O, which may reduce the thermal stresses formed when cooling the glass articles and, therefore, improve the quality of the glass articles. In embodiments, the glass may contain sodium oxide (Na₂O) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 15.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain Na₂O in an amount greater than or equal to 0.0 mol. %, greater than or equal to 5.0 mol. %, or greater than or equal to 10.0 mol. %. In some other embodiments, the glass composition may contain Na₂O in an amount less than or equal to 15.0 mol. %, less than or equal to 13.0 mol. %, less than or equal to 11.5 mol. %, less than or equal to 10.0 mol. %, less than or equal to 7.1 mol. %, or less than or equal to 5.0 mol. %. In some more embodiments, the glass composition may contain Na₂O in an amount greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 13.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 11.5 mol. %, greater than or equal to 0.02 mol. % and less than or equal to 7.13 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 7.1 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 13.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 11.5 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 7.1 mol. %, greater than or equal to 7.1 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 7.1 mol. % and less than or equal to 13.0 mol. %, greater than or equal to 7.1 mol. % and less than or equal to 11.5 mol. %, greater than or equal to 7.1 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 5.5 mol. % and less than or equal to 11.0 mol. %, greater than or equal to 7.5 mol. % and less than or equal to 13.7 mol. %, or greater than or equal to 5.0 mol. % and less than or equal to 11.5 mol. %.

Glass composition may include lithium oxide (Li₂O). Lithium oxide provides the highest ratio of the refractive index to density of glasses among the known monovalent metal oxides. Also, in some embodiments, Li₂O may help to increase the solubility of Nb₂O₅ and TiO₂, which additionally increases the refractive index at comparably low density. In addition, lithium oxide may hasten the process of bleaching the glasses. However, it was empirically found that in some embodiments, addition of Li₂O, even in small concentrations, may decrease the glass-forming ability of glasses by causing crystallization or liquid-liquid phase separation of glass-forming melts when cooling. Therefore, the amount of Li₂O in glasses of the present disclosure is limited. However, the mentioned undesirable effects of Li₂O are difficult to predict; for this reason, the exact boundary of Li₂O in the embodiments may be very different. In particular, in some embodiments, the glasses may be substantially free of Li₂O. In embodiments, the glass may contain lithium oxide (Li₂O) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 10.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain Li₂O in an amount greater than or equal to 0.0 mol. %, greater than or equal to 0.5 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 1.5 mol. %, greater than or equal to 2.5 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 7.5 mol. %, greater than or equal to 8.5 mol. %, greater than or equal to 9.0 mol. %, or greater than or equal to 9.5 mol. %. In some other embodiments, the glass composition may contain Li₂O in an amount less than or equal to 10.0 mol. %, less than or equal to 9.5 mol. %, less than or equal to 9.0 mol. %, less than or equal to 8.5 mol. %, less than or equal to 7.5 mol. %, less than or equal to 5.0 mol. %, less than or equal to 4.0 mol. %, less than or equal to 2.5 mol. %, less than or equal to 1.5 mol. %, less than or equal to 1.0 mol. %, or less than or equal to 0.5 mol. %. In some more embodiments, the glass composition may contain Li₂O in an amount greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 8.5 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 1.28 mol. % and less than or equal to 4.1 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 8.5 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 8.5 mol. %, greater than or equal to 1.5 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 9.0 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 9.5 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 9.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 8.5 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 1.4 mol. % and less than or equal to 9.0 mol. %, greater than or equal to 4.5 mol. % and less than or equal to 7.4 mol. %, or greater than or equal to 5.6 mol. % and less than or equal to 8.7 mol. %.

Glass composition may include alumina (Al₂O₃). Alumina may increase the viscosity of glass-forming melts at high temperature, which may reduce the critical cooling rate and improve the glass-forming ability. However, in high-index phosphate glasses, addition of Al₂O₃ may cause crystallization of refractory minerals, such as aluminum phosphate (AlPO₄), aluminum titanate (Al₂TiO₅), aluminum niobate (AlNbO₄) and others, in the glass-forming melts when cooling. Accordingly, the amount of Al₂O₃ in glasses of the present disclosure is limited, or glasses may be substantially free of Al₂O₃. In embodiments, the glass may contain alumina (Al₂O₃) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 10.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain Al₂O₃ in an amount greater than or equal to 0.0 mol. %, greater than or equal to 0.5 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 1.5 mol. %, greater than or equal to 2.5 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 7.5 mol. %, greater than or equal to 8.5 mol. %, greater than or equal to 9.0 mol. %, or greater than or equal to 9.5 mol. %. In some other embodiments, the glass composition may contain Al₂O₃ in an amount less than or equal to 10.0 mol. %, less than or equal to 9.5 mol. %, less than or equal to 9.0 mol. %, less than or equal to 8.5 mol. %, less than or equal to 7.5 mol. %, less than or equal to 5.0 mol. %, less than or equal to 2.5 mol. %, less than or equal to 1.5 mol. %, less than or equal to 1.0 mol. %, or less than or equal to 0.5 mol. %. In some more embodiments, the glass composition may contain Al₂O₃ in an amount greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 2.5 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 0.5 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 8.5 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 2.5 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 9.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 2.5 mol. %, greater than or equal to 1.5 mol. % and less than or equal to 9.0 mol. %, greater than or equal to 1.5 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 1.5 mol. % and less than or equal to 2.5 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 8.5 mol. %, greater than or equal to 7.5 mol. % and less than or equal to 9.0 mol. %, greater than or equal to 7.5 mol. % and less than or equal to 8.5 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 4.9 mol. %, greater than or equal to 1.4 mol. % and less than or equal to 5.0 mol. %, or greater than or equal to 6.0 mol. % and less than or equal to 9.5 mol. %.

Glass composition may include vanadia (V₂O₅). Vanadia provides the highest ratio of the refractive index to density among all oxides. However, vanadia may cause undesirable dark or even black coloring and may also raise environmental concerns. For these reasons, the content of vanadia in the glasses of the present disclosure is limited, or glass compositions may be free of V₂O₅. In embodiments, the glass may contain vanadia (V₂O₅) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 1.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain V₂O₅ in an amount greater than or equal to 0.0 mol. %, greater than or equal to 0.05 mol. %, greater than or equal to 0.10 mol. %, greater than or equal to 0.15 mol. %, greater than or equal to 0.25 mol. %, greater than or equal to 0.5 mol. %, greater than or equal to 0.75 mol. %, greater than or equal to 0.85 mol. %, greater than or equal to 0.9 mol. %, or greater than or equal to 0.95 mol. %. In some other embodiments, the glass composition may contain V₂O₅ in an amount less than or equal to 1.0 mol. %, less than or equal to 0.95 mol. %, less than or equal to 0.9 mol. %, less than or equal to 0.85 mol. %, less than or equal to 0.75 mol. %, less than or equal to 0.5 mol. %, less than or equal to 0.25 mol. %, less than or equal to 0.15 mol. %, less than or equal to 0.10 mol. %, or less than or equal to 0.05 mol. %. In some more embodiments, the glass composition may contain V₂O₅ in an amount greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. %, greater than or equal to 0.05 mol. % and less than or equal to 1.0 mol. %, greater than or equal to 0.05 mol. % and less than or equal to 0.85 mol. %, greater than or equal to 0.10 mol. % and less than or equal to 0.9 mol. %, greater than or equal to 0.10 mol. % and less than or equal to 0.75 mol. %, greater than or equal to 0.10 mol. % and less than or equal to 0.25 mol. %, greater than or equal to 0.15 mol. % and less than or equal to 0.9 mol. %, greater than or equal to 0.15 mol. % and less than or equal to 0.75 mol. %, greater than or equal to 0.15 mol. % and less than or equal to 0.25 mol. %, greater than or equal to 0.25 mol. % and less than or equal to 1.0 mol. %, greater than or equal to 0.25 mol. % and less than or equal to 0.9 mol. %, greater than or equal to 0.25 mol. % and less than or equal to 0.75 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 0.95 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 0.9 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 0.85 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 0.75 mol. %, greater than or equal to 0.75 mol. % and less than or equal to 0.95 mol. %, greater than or equal to 0.75 mol. % and less than or equal to 0.9 mol. %, greater than or equal to 0.75 mol. % and less than or equal to 0.85 mol. %, greater than or equal to 0.26 mol. % and less than or equal to 0.86 mol. %, greater than or equal to 0.14 mol. % and less than or equal to 0.99 mol. %, or greater than or equal to 0.42 mol. % and less than or equal to 0.73 mol. %.

Glass composition may include tungsten oxide (WO₃). WO₃ provides high refractive index without significantly increasing density or causing undesirable coloring. However, at high concentrations of WO₃, such as greater than or equal to 10.0 mol. %, or greater than or equal to 20.0 mol. %, or like, the liquidus temperature tends to rise, and the viscosity at the liquidus temperature drops, making it difficult to avoid crystallization of melts when cooling and/or to obtain high-quality optical glass. Accordingly, the content of WO₃ should be limited, or glass compositions may be free of WO₃. In embodiments, the glass may contain tungsten oxide (WO₃) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 10.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain WO₃ in an amount greater than or equal to 0.0 mol. %, greater than or equal to 2.5 mol. %, greater than or equal to 5.0 mol. %, or greater than or equal to 7.5 mol. %. In some other embodiments, the glass composition may contain WO₃ in an amount less than or equal to 10.0 mol. %, less than or equal to 7.5 mol. %, less than or equal to 5.0 mol. %, less than or equal to 3.0 mol. %, or less than or equal to 2.5 mol. %. In some more embodiments, the glass composition may contain WO₃ in an amount greater than or equal to 0.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 2.5 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 2.5 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 7.5 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 3.2 mol. %, greater than or equal to 3.5 mol. % and less than or equal to 7.6 mol. %, or greater than or equal to 2.5 mol. % and less than or equal to 5.6 mol. %.

Glass composition may include tantalum oxide (Ta₂O₅). Tantalum oxide increases the refractive index while maintaining an acceptable density without reducing the blue transmittance. However, when added to a glass composition, sometimes even in small amounts, Ta₂O₅ may cause crystallization of refractory minerals, which may increase the liquidus temperature and, therefore, reduce the glass-forming ability. Accordingly, the content of tantalum oxide should be limited, or glass compositions may be free of Ta₂O₅. In embodiments, the glass may contain tantalum oxide (Ta₂O₅) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 5.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain Ta₂O₅ in an amount greater than or equal to 0.0 mol. %, greater than or equal to 0.03 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 3.0 mol. %, or greater than or equal to 4.0 mol. %. In some other embodiments, the glass composition may contain Ta₂O₅ in an amount less than or equal to 5.0 mol. %, less than or equal to 4.0 mol. %, less than or equal to 3.0 mol. %, less than or equal to 2.0 mol. %, less than or equal to 1.0 mol. %, or less than or equal to 0.04 mol. %. In some more embodiments, the glass composition may contain Ta₂O₅ in an amount greater than or equal to 0.0 mol. % and less than or equal to 2.0 mol. %, greater than or equal to 0.03 mol. % and less than or equal to 0.04 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. %, greater than or equal to 0.04 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 0.04 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 0.04 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 0.04 mol. % and less than or equal to 2.0 mol. %, greater than or equal to 0.04 mol. % and less than or equal to 1.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 2.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 3.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 4.0 mol. %, or greater than or equal to 2.0 mol. % and less than or equal to 5.0 mol. %.

Glass composition may include bismuth oxide (Bi₂O₃). Bi₂O₃ provides very high refractive index, higher than any other components considered herein, but leads to increases in density. Sometimes it may provide undesirable coloring. Also, it may decrease the viscosity of melts at high temperatures, which may cause crystallization of the melts when cooling. This effect is especially significant at high concentrations of Bi₂O₃, such as, for example, greater than 20.0 mol. %, or greater than 26.0 mol. %, or higher. Accordingly, the content of bismuth oxide should be limited, or glass compositions may be free of Bi₂O₃. In embodiments, the glass may contain bismuth oxide (Bi₂O₃) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 15.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain Bi₂O₃ in an amount greater than or equal to 0.0 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 3.0 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 10.0 mol. %, greater than or equal to 12.0 mol. %, greater than or equal to 13.0 mol. %, or greater than or equal to 14.0 mol. %. In some other embodiments, the glass composition may contain Bi₂O₃ in an amount less than or equal to 15.0 mol. %, less than or equal to 23.0 mol. %, less than or equal to 20.0 mol. %, less than or equal to 15.0 mol. %, less than or equal to 14.0 mol. %, less than or equal to 13.0 mol. %, less than or equal to 12.0 mol. %, less than or equal to 10.0 mol. %, less than or equal to 5.0 mol. %, less than or equal to 4.0 mol. %, less than or equal to 3.0 mol. %, less than or equal to 2.0 mol. %, or less than or equal to 1.0 mol. %. In some more embodiments, the glass composition may contain Bi₂O₃ in an amount greater than or equal to 0.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 23.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 14.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 14.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 4.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 12.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 5.5 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 0.8 mol. % and less than or equal to 8.1 mol. %, or greater than or equal to 2.5 mol. % and less than or equal to 8.0 mol. %.

Glass composition may include titania (TiO₂). High refractive index glasses typically include species, such as TiO₂ and Nb₂O₅, that absorb at least a portion of optical light, particularly light in the blue and near-UV regions of the electromagnetic spectrum. In embodiments of the present disclosure, the transmittance of the glass may be characterized for different wavelengths within the range of from about 300 nm to 2300 nm. High transmission in the visible and near-UV range (blue region) is particularly desirable in some applications. High transmittance in the blue can be challenging to achieve in high refractive index glasses. High level of TiO₂ and/or Nb₂O₅ that are typically used in glasses to increase refractive index tend to decrease the transmittance in the near-UV region and shift the UV cut-off to higher wavelengths. Accordingly, the amount of TiO₂ in the glass compositions of the present disclosure is limited. In embodiments, the glass may contain titania (TiO₂) in an amount greater than or equal to 0.3 mol. % to less than or equal to 40.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain TiO₂ in an amount greater than or equal to 0.3 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 3.0 mol. %, greater than or equal to 4.0 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 7.0 mol. %, greater than or equal to 10.0 mol. %, greater than or equal to 11.0 mol. %, greater than or equal to 14.9 mol. %, greater than or equal to 20.0 mol. %, greater than or equal to 25.0 mol. %, greater than or equal to 30.0 mol. %, greater than or equal to 35.0 mol. %, greater than or equal to 37.0 mol. %, greater than or equal to 38.0 mol. %, or greater than or equal to 39.0 mol. %. In some other embodiments, the glass composition may contain TiO₂ in an amount less than or equal to 40.0 mol. %, less than or equal to 39.0 mol. %, less than or equal to 38.0 mol. %, less than or equal to 37.0 mol. %, less than or equal to 35.0 mol. %, less than or equal to 32.0 mol. %, less than or equal to 30.0 mol. %, less than or equal to 25.0 mol. %, less than or equal to 22.2 mol. %, less than or equal to 20.0 mol. %, less than or equal to 15.0 mol. %, less than or equal to 10.0 mol. %, less than or equal to 5.0 mol. %, less than or equal to 3.0 mol. %, less than or equal to 2.0 mol. %, or less than or equal to 1.0 mol. %. In some more embodiments, the glass composition may contain TiO₂ in an amount greater than or equal to 0.3 mol. % and less than or equal to 40.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 40.0 mol. %, greater than or equal to 7.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 11.0 mol. % and less than or equal to 32.0 mol. %, greater than or equal to 14.94 mol. % and less than or equal to 22.17 mol. %, greater than or equal to 0.3 mol. % and less than or equal to 32.0 mol. %, greater than or equal to 0.3 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 0.3 mol. % and less than or equal to 1.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 32.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 22.2 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 22.2 mol. %, greater than or equal to 3.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 22.2 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 40.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 37.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 37.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 20.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 22.2 mol. % and less than or equal to 38.0 mol. %, greater than or equal to 22.2 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 25.0 mol. % and less than or equal to 38.0 mol. %, greater than or equal to 25.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 25.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 8.0 mol. % and less than or equal to 19.0 mol. %, greater than or equal to 20.0 mol. % and less than or equal to 33.0 mol. %, or greater than or equal to 20.0 mol. % and less than or equal to 37.0 mol. %.

Glass composition may include niobia (Nb₂O₅). Niobia, like titania, can be used in some aspects of the present disclosure to increase the refractive index of glass while also maintaining a low density. However, niobia can introduce a yellow coloring to the glass that cannot be bleached in the same manner as titania, which can result in a loss of transmittance, particularly in the blue and UV range. Niobia, like titania, may cause crystallization and/or phase separation of the melt. In some cases, niobia may provide the glass with a high optical dispersion, which can be significantly higher than that induced by titania and some other high index components, when added in similar concentrations. The effects of niobia can be affected by the other components of the glass, and thus it can be challenging to determine an exact limit for niobia. In some embodiments, the glasses may be substantially free of Nb₂O₅; in this case, its function is performed by other species, such as, for example, TiO₂. In embodiments, the glass may contain niobia (Nb₂O₅) in an amount from greater than or equal to 0.0 mol. % to less than or equal to 50.0 mol. % and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may contain Nb₂O₅ in an amount greater than or equal to 0.0 mol. %, greater than or equal to 1.0 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 4.0 mol. %, greater than or equal to 6.0 mol. %, greater than or equal to 10.0 mol. %, greater than or equal to 20.0 mol. %, greater than or equal to 25.0 mol. %, greater than or equal to 27.5 mol. %, greater than or equal to 28.0 mol. %, greater than or equal to 30.0 mol. %, greater than or equal to 40.0 mol. %, greater than or equal to 44.0 mol. %, greater than or equal to 46.0 mol. %, or greater than or equal to 48.0 mol. %. In some other embodiments, the glass composition may contain Nb₂O₅ in an amount less than or equal to 50.0 mol. %, less than or equal to 48.0 mol. %, less than or equal to 46.0 mol. %, less than or equal to 44.0 mol. %, less than or equal to 42.0 mol. %, less than or equal to 40.0 mol. %, less than or equal to 39.0 mol. %, less than or equal to 30.0 mol. %, less than or equal to 20.0 mol. %, less than or equal to 10.0 mol. %, less than or equal to 6.0 mol. %, less than or equal to 4.0 mol. %, or less than or equal to 2.0 mol. %. In some more embodiments, the glass composition may contain Nb₂O₅ in an amount greater than or equal to 0.0 mol. % and less than or equal to 50.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 50.0 mol. %, greater than or equal to 20.0 mol. % and less than or equal to 50.0 mol. %, greater than or equal to 25.0 mol. % and less than or equal to 44.0 mol. %, greater than or equal to 27.5 mol. % and less than or equal to 42.0 mol. %, greater than or equal to 27.99 mol. % and less than or equal to 38.99 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 42.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 50.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 42.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 44.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 39.0 mol. %, greater than or equal to 4.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 6.0 mol. % and less than or equal to 44.0 mol. %, greater than or equal to 6.0 mol. % and less than or equal to 39.0 mol. %, greater than or equal to 6.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 39.0 mol. %, greater than or equal to 20.0 mol. % and less than or equal to 46.0 mol. %, greater than or equal to 20.0 mol. % and less than or equal to 42.0 mol. %, greater than or equal to 30.0 mol. % and less than or equal to 46.0 mol. %, greater than or equal to 30.0 mol. % and less than or equal to 39.0 mol. %, greater than or equal to 39.0 mol. % and less than or equal to 42.0 mol. %, greater than or equal to 40.0 mol. % and less than or equal to 48.0 mol. %, greater than or equal to 40.0 mol. % and less than or equal to 42.0 mol. %, greater than or equal to 8.0 mol. % and less than or equal to 38.0 mol. %, greater than or equal to 14.0 mol. % and less than or equal to 46.0 mol. %, or greater than or equal to 15.0 mol. % and less than or equal to 36.0 mol. %.

In some embodiments, the glass composition may have a sum of CaO+SrO greater than or equal to 0.0 mol. %, greater than or equal to 0.5 mol. %, greater than or equal to 2.0 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 10.0 mol. %, greater than or equal to 15.0 mol. %, greater than or equal to 20.0 mol. %, greater than or equal to 25.0 mol. %, or greater than or equal to 30.0 mol. %. In some other embodiments, the glass composition may have a sum of CaO+SrO less than or equal to 35.0 mol. %, less than or equal to 30.0 mol. %, less than or equal to 25.0 mol. %, less than or equal to 20.0 mol. %, less than or equal to 15.0 mol. %, less than or equal to 10.0 mol. %, or less than or equal to 5.0 mol. %. In some more embodiments, the glass composition may have a sum of CaO+SrO greater than or equal to 0.5 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 25.0 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 0.5 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 2.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 25.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 35.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 30.0 mol. %, greater than or equal to 15.0 mol. % and less than or equal to 25.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 11.0 mol. % and less than or equal to 23.0 mol. %, or greater than or equal to 24.0 mol. % and less than or equal to 34.0 mol. %.

In some embodiments, the glass composition may have a sum of SiO₂+GeO₂ greater than or equal to 0.0 mol. %, greater than or equal to 5.0 mol. %, or greater than or equal to 10.0 mol. %. In some other embodiments, the glass composition may have a sum of SiO₂+GeO₂ less than or equal to 15.0 mol. %, less than or equal to 10.0 mol. %, or less than or equal to 5.0 mol. %. In some more embodiments, the glass composition may have a sum of SiO₂+GeO₂ greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 5.5 mol. % and less than or equal to 11.5 mol. %, greater than or equal to 3.5 mol. % and less than or equal to 10.5 mol. %, or greater than or equal to 6.7 mol. % and less than or equal to 13.5 mol. %.

In some embodiments, the glass composition may have a sum of TeO₂+SnO₂+SnO greater than or equal to 0.0 mol. %, greater than or equal to 5.0 mol. %, greater than or equal to 10.0 mol. %, or greater than or equal to 15.0 mol. %. In some other embodiments, the glass composition may have a sum of TeO₂+SnO₂+SnO less than or equal to 20.0 mol. %, less than or equal to 15.0 mol. %, less than or equal to 10.0 mol. %, or less than or equal to 5.0 mol. %. In some more embodiments, the glass composition may have a sum of TeO₂+SnO₂+SnO greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 5.0 mol. % and less than or equal to 10.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 20.0 mol. %, greater than or equal to 10.0 mol. % and less than or equal to 15.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 9.0 mol. %, greater than or equal to 1.0 mol. % and less than or equal to 14.0 mol. %, or greater than or equal to 5.0 mol. % and less than or equal to 17.0 mol. %.

In some embodiments, the glass may have a density d_(RT) from greater than or equal to 3.40 g/cm³ to less than or equal to 5.00 g/cm³ and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may have a density d_(RT) greater than or equal to 3.40 g/cm³, greater than or equal to 3.50 g/cm³, greater than or equal to 3.60 g/cm³, greater than or equal to 3.68 g/cm³, greater than or equal to 3.70 g/cm³, greater than or equal to 3.75 g/cm³, greater than or equal to 4.25 g/cm³, greater than or equal to 4.70 g/cm³, greater than or equal to 4.75 g/cm³, greater than or equal to 4.80 g/cm³, or greater than or equal to 4.90 g/cm³. In some other embodiments, the glass composition may have a density d_(RT) less than or equal to 5.00 g/cm³, less than or equal to 4.90 g/cm³, less than or equal to 4.80 g/cm³, less than or equal to 4.75 g/cm³, less than or equal to 4.70 g/cm³, less than or equal to 4.30 g/cm³, less than or equal to 4.25 g/cm³, less than or equal to 4.20 g/cm³, less than or equal to 4.00 g/cm³, less than or equal to 3.87 g/cm³, less than or equal to 3.75 g/cm³, less than or equal to 3.70 g/cm³, less than or equal to 3.60 g/cm³, or less than or equal to 3.50 g/cm³. In some more embodiments, the glass composition may have a density d_(RT) greater than or equal to 3.40 g/cm³ to 5.00 g/cm³, greater than or equal to 3.40 g/cm³ to 4.70 g/cm³, greater than or equal to 3.50 g/cm³ to 4.70 g/cm³, greater than or equal to 3.50 g/cm³ to 4.00 g/cm³, greater than or equal to 3.60 g/cm³ to 4.70 g/cm³, greater than or equal to 3.60 g/cm³ to 4.00 g/cm³, greater than or equal to 3.70 g/cm³ to 4.75 g/cm³, greater than or equal to 3.70 g/cm³ to 4.25 g/cm³, greater than or equal to 3.75 g/cm³ to 5.00 g/cm³, greater than or equal to 3.75 g/cm³ to 4.25 g/cm³, greater than or equal to 3.87 g/cm³ to 4.75 g/cm³, greater than or equal to 4.00 g/cm³ to 5.00 g/cm³, greater than or equal to 4.00 g/cm³ to 4.70 g/cm³, greater than or equal to 3.62 g/cm³ to 4.50 g/cm³, greater than or equal to 4.15 g/cm³ to 4.65 g/cm³, or greater than or equal to 3.98 g/cm³ to 4.81 g/cm³.

In some embodiments, the glass may have a refractive index n_(d) from greater than or equal to 1.80 to less than or equal to 2.03 and all ranges and sub-ranges between the foregoing values. In some embodiments, the glass composition may have a refractive index n_(d) greater than or equal to 1.80, greater than or equal to 1.82, greater than or equal to 1.84, greater than or equal to 1.85, greater than or equal to 1.90, greater than or equal to 1.95, greater than or equal to 1.97, greater than or equal to 1.98, greater than or equal to 1.99, greater than or equal to 2.00, or greater than or equal to 2.01. In some other embodiments, the glass composition may have a refractive index n_(d) less than or equal to 2.03, less than or equal to 2.01, less than or equal to 2.00, less than or equal to 1.99, less than or equal to 1.97, less than or equal to 1.90, less than or equal to 1.84, or less than or equal to 1.82. In some more embodiments, the glass composition may have a refractive index n_(d) greater than or equal to 1.80 to 2.03, greater than or equal to 1.80 to 2.00, greater than or equal to 1.82 to 2.03, greater than or equal to 1.82 to 2.00, greater than or equal to 1.82 to 1.97, greater than or equal to 1.84 to 2.03, greater than or equal to 1.84 to 2.00, greater than or equal to 1.84 to 1.97, greater than or equal to 1.90 to 2.03, greater than or equal to 1.90 to 2.01, greater than or equal to 1.90 to 2.00, greater than or equal to 1.90 to 1.99, greater than or equal to 1.90 to 1.97, greater than or equal to 1.99 to 2.03, greater than or equal to 1.88 to 1.99, greater than or equal to 1.85 to 1.91, or greater than or equal to 1.95 to 2.02.

In some embodiments, the glass composition may have a quantity n_(d)−(1.83+0.04*d_(RT)) greater than or equal to 0.00.

In some embodiments, the glass composition may have a quantity n_(d)−(1.85+0.04*d_(RT)) greater than or equal to 0.00.

In some embodiments, the glass composition may have a quantity n_(d)−(1.83+0.04*d_(RT))−(−0.06+0.0013*(TiO₂+Nb₂O₅)) greater than or equal to 0.00.

In some embodiments, the glass composition may have a quantity n_(d)−(1.83+0.04*d_(RT))−(−0.05+0.0013*(TiO₂+Nb₂O₅)) greater than or equal to 0.00.

Refractive index n_(d) and density d_(RT) are properties of a glass that can be predicted from the glass composition. A linear regression analysis of the exemplary glasses of the present disclosure in the EXAMPLES section below and other glass compositions reported in the literature was performed to determine equations that can predict the composition dependences of refractive index at 587.56 nm and density at room temperature.

The training dataset of glass compositions satisfying the criteria specified in Table 1 below and having measured values of the properties of interest, about 100 glass compositions for each property (n_(d) and d_(RT)), was randomly selected from the literature data presented in the publicly available SciGlass Information System database and from the Exemplary Glasses from the embodiments presented herein. The linear regression analysis on the above-specified dataset was used to determine the formulas, with the exclusion of insignificant variables and outliers. The resulting formulas are presented in Table 2 below. Another part of glass compositions satisfying the same criteria was used as a validation set to evaluate the ability to interpolate within predefined compositional limits, which corresponds to the standard deviations specified in the Table 2. An external dataset of prior art glass compositions, also randomly selected from the SciGlass Information System database, was used to evaluate the ability to predict the properties outside of the specified compositional limits with a reasonable accuracy. Multiple iterations of this process were performed in order to determine the best variant for each property, corresponding to the above-mentioned regression formulas specified in the Table 2.

The data for the Comparative Glass compositions used in the linear regression modeling, including the training dataset, validation dataset and external dataset were obtained from the publicly available SciGlass Information System database. Formulas (I) and (II) below were obtained from the linear regression analysis and used to predict the refractive index n_(d) and density d_(RT), respectively, of the glasses: P _(n)=−0.0043794*P₂O₅+0.0072428*Nb₂O₅+0.0037304*TiO₂−0.00039553*BaO−0.0032012*K₂O−0.00060689*CaO−0.0024218*Na₂O−0.0014988*Li₂O+0.0028587*WO₃+0.0083295*Bi₂O₃−0.0031637*B₂O₃−0.0030702*SiO₂−0.00030248*ZnO+0.0020025*ZrO₂−0.0018173*MgO−0.0032886*Al₂O₃+0.0024221*TeO₂+0.0038137*PbO−0.0016392*GeO₂+0.0063024*Tl₂O+0.0048765*Ag₂O+1.81451,  (I) P _(d)[g/cm³]=3.98457−0.015773*Al₂O₃−0.014501*B₂O₃+0.019328*BaO+0.060758*Bi₂O₃−0.0012685*CaO+0.023111*CdO+0.0053184*Cs₂O+0.011488*Ga₂O₃−0.0015416*GeO₂−0.013342*K₂O+0.058319*La₂O₃−0.007918*Li₂O−0.0021423*MgO−0.0024413*MoO₃−0.0082226*Na₂O+0.0084961*Nb₂O₅−0.020501*P₂O₅+0.038898*PbO−0.012720*SiO₂+0.013948*SrO+0.047924*Ta₂O₅+0.011248*TeO₂−0.0092491*V₂O₅+0.028913*WO₃+0.0074702*ZnO+0.0096721*ZrO₂.

In Formulas (I) and (II) and Tables 1 and 2, refractive index parameter P_(n) is a parameter that predicts the refractive index n_(d) from the concentrations of the components of the glass composition expressed in terms of mol. %; and density parameter P_(d) is a parameter that predicts the density d_(RT) from the concentrations of the components of the glass composition expressed in terms of mol. %. In Formulas (I) and (II), each component of the glass composition is listed in terms of its chemical formula, where the chemical formula refers to the concentration of the component expressed in mol. %. For example, for purposes of Formulas (I) and (II), P₂O₅ refers to the concentration of P₂O₅, expressed in mol. %, in the glass composition. It is understood that not all components listed in Formulas (I) and (II) are necessarily present in a particular glass composition and that Formulas (I) and (II) are equally valid for glass compositions that contain less than all of the components listed in the formulas. It is further understood that Formulas (I) and (II) are also valid for glass compositions within the scope and claims of the present disclosure that contain components in addition to the components listed in the formulas. If a component listed in Formulas (I) and (II) is absent in a particular glass composition, the concentration of the component in the glass composition is 0 mol. % and the contribution of the component to the value calculated from the formulas is zero. In Table 1, R_(m)O_(n) is total sum of all oxides.

TABLE 1 Composition Space Used for Modeling Property n_(d) d_(RT) Component limits Min, Max, Min, Max, mol. % mol. % mol. % mol. % Nb₂O₅ 5 60 0 60 P₂O₅ 10 30 10 30 TiO₂ 0 40 0 40 CaO 0 40 0 40 K₂O 0 20 0 20 BaO 0 20 0 20 Na₂O 0 30 0 30 SiO₂ 0 20 0 20 ZnO 0 20 0 20 Li₂O 0 10 0 10 SrO 0 30 0 30 ZrO₂ 0 10 0 10 WO₃ 0 15 0 15 MgO 0 10 0 10 B₂O₃ 0 10 0 10 Al₂O₃ 0  5 0  5 R_(m)O_(n) 99 Not 99 Not limited limited TeO₂ + PbO + GeO₂ + Tl₂O 0 20 0 20 Ag₂O + Cu₂O + CuO + 0 15 0 15 As₂O₃ + Sb₂O₃ P₂O₅ − SiO₂ 10 Not 10 Not limited limited TiO₂ + Nb₂O₅ + WO₃ + GeO₂ + 25 Not Not Not Bi₂O₃ + TeO₂ limited limited limited TiO₂ + Nb₂O₅ + WO₃ + V₂O₅ + Not Not 25 Not GeO₂ + Bi₂O₃ + TeO₂ limited limited limited V₂O₅ Not Not 0 80 limited limited Other species 0 Not 0 Not limited limited

TABLE 2 Property prediction models Abbre- Predicting Regression Standard Property viation Unit Parameter Formula error Refractive n_(d) P_(n) Formula (I) 0.016 index at 587.56 nm Density at d_(RT) P_(d) Formula (II) 0.20 room temperature

FIG. 1 is a plot of the parameter P_(n) calculated by Formula (I) as a function of measured refractive index n_(d) for some Literature Glasses (“Comp. Glasses”) and some Exemplary Glasses (“Ex. Glasses”). As illustrated by the data in FIG. 1, the compositional dependence of the parameter P_(n) had an error within a range of ±0.016 unit of the measured n_(d) for the majority of glasses, that corresponds to the standard error specified in Table 2.

FIG. 2 is a plot of the parameter P_(d) calculated by Formula (II) as a function of measured density d_(RT) for some Literature Glasses (“Comp. Glasses”) and some Exemplary Glasses (“Ex. Glasses”). As illustrated by the data in FIG. 2, the compositional dependence of the parameter P_(d) had an error within a range of ±0.20 unit of the measured d_(RT) for the majority of glasses, that corresponds to the standard error specified in Table 2.

Table 3 identifies the combination of components and their respective amounts according to some embodiments of the present disclosure. The Exemplary Glasses A in Table 3 may include additional components according to any aspects of the present disclosure as described herein.

TABLE 3 Exemplary Glasses A Composition Amount (mol. %) P₂O₅ 10.0 to 40.0 mol. % TiO₂ 1.0 to 40.0 mol. % K₂O 0.5 to 35.0 mol. % Nb₂O₅ 0.0 to 50.0 mol. % MgO 0.0 to 15.0 mol. % Al₂O₃ 0.0 to 10.0 mol. % Sum of (CaO + SrO) 0.5 to 35.0 mol. % Sum of (TeO₂ + SnO₂ + SnO) 0.0 to 20.0 mol. % Sum of (SiO₂ + GeO₂) 0.0 to 15.0 mol. %

Exemplary Glasses A according to embodiments of the present disclosure may have a density at room temperature d_(RT) of less than or equal to 5 g/cm³.

According to some embodiments of the present disclosure, Exemplary Glasses A may also have a refractive index n_(d) of greater than or equal to 1.9.

According to some embodiments of the present disclosure, Exemplary Glasses A may also satisfy the following formula: n _(d)−(1.83+0.04*d _(RT))>0.00, where n_(d) is a refractive index at 587.56 nm, and d_(RT) is a density at room temperature expressed in units of g/cm³.

According to some embodiments of the present disclosure, Exemplary Glasses A may also satisfy the following formula: n _(d)−(1.85+0.04*d _(RT))>0.00, where n_(d) is a refractive index at 587.56 nm, and d_(RT) is a density at room temperature expressed in units of g/cm³.

Table 4 identifies the combination of components and their respective amounts according to some embodiments of the present disclosure. The Exemplary Glasses B in Table 4 may include additional components according to any aspects of the present disclosure as described herein.

TABLE 4 Exemplary Glasses B Composition Amount (mol. %) P₂O₅ 17.0 to 27.0 mol. % Nb₂O₅ 1.0 to 50.0 mol. % TiO₂ 1.0 to 40.0 mol. % K₂O 0.0 to 35.0 mol. % CaO 0.0 to 35.0 mol. % MgO 0.0 to 15.0 mol. % Bi₂O₃ 0.0 to 15.0 mol. % Al₂O₃ 0.0 to 10.0 mol. % Total sum of divalent metal oxides RO ≥5.0 mol. % Total sum of alkali metal oxides Alk₂O ≥5.0 mol. % Sum of (SiO₂ + GeO₂) 0.0 to 15.0 mol. % Sum of (TeO₂ + SnO₂ + SnO) 0.0 to 10.0 mol. %

Exemplary Glasses B according to embodiments of the present disclosure may satisfy the following formula: n _(d)−(1.83+0.04*d _(RT))−(−0.06+0.0013*(TiO₂+Nb₂O₅))>0.00, where n_(d) is a refractive index at 587.56 nm, TiO₂ refers to the concentration of TiO₂ expressed in units of mol. %, Nb₂O₅ refers to the concentration of Nb₂O₅ expressed in units of mol. %, and d_(RT) is a density at room temperature expressed in units of g/cm³.

According to some embodiments of the present disclosure, Exemplary Glasses B may also satisfy the following formula: n _(d)−(1.83+0.04*d _(RT))−(−0.05+0.0013*(TiO₂+Nb₂O₅))>0.00, where n_(d) is a refractive index at 587.56 nm, TiO₂ refers to the concentration of TiO₂ expressed in units of mol. %, Nb₂O₅ refers to the concentration of Nb₂O₅ expressed in units of mol. %, and d_(RT) is a density at room temperature expressed in units of g/cm³.

Examples

The following examples describe various features and advantages provided by the disclosure, and are in no way intended to limit the invention and appended claims.

To prepare the glass samples for some exemplary glasses of the present disclosure, about 15 grams of each sample (content of target species was more than 99.99 wt %) was melted from batch raw materials at a temperature of about 1300° C. in platinum or platinum-rhodium crucibles (Pt:Rh=80:20) for 1 hour. Two controlled cooling conditions were applied. In the first condition (referred to as “15 min test” or “15 min devit test”), the sample was left in the furnace after melting and the furnace was turned off to allow the sample to cool slowly in air. Under these conditions, it takes about 15 min for the samples to cool from 1100° C. to 500° C. In the second condition (referred to as “2.5 min test” or “2.5 min devit test”), the furnace was turned off and the sample was removed from the furnace at a temperature of 1100° C. and allowed to cool in air at room temperature. Under these conditions, it takes about 2.5 min for the samples to cool from 1100° C. to 500° C. Temperature readings were obtained by direct reading of the furnace temperature or using an IR camera reading with calibration scaling. The first condition (15 min test) approximately corresponds to the cooling rate of up to 300° C./min at a temperature of 1000° C. and the second test approximately corresponds to the cooling rate of up to 600° C./min at 1000° C. (near to this temperature, the cooling rate approached the maximum). When the temperature is lower, the cooling rate also decreases significantly. Typical schedules of the first and second cooling regimes are shown in FIG. 3. For these samples, observations referred to as “15-min devit test” and “2.5-min devit test”, are specified in Table 5 below; the observation “1” is used to denote that a glass composition passed the indicated devit test, where a composition is deemed to have passed the indicated devit test if the volume fraction of the glassy part of the sample is more than that of the crystals. The observation “0” is used to denote that the crystal volume fraction is more than that of the glassy part.

To prepare other glass samples for exemplary glasses of the present disclosure, unless otherwise specified, one kilogram of batch was prepared in a pure platinum crucible. The crucible was placed in a furnace set at a temperature of 1250° C., after which, the temperature in the furnace was raised to 1300° C. and held at 1300° C. for 2 hours. The furnace temperature was then reduced to 1250° C. and the glass was allowed to equilibrate at this temperature for an hour before being poured on a steel table followed by annealing at Tg for an hour. For some compositions, slight adjustments to temperatures and times were made to ensure complete melting. For example, for some compositions melting temperatures of 1350

C or 1400

C and/or hold times of up to 4 hours were used.

Some sample melts were also melted in a “one liter” platinum crucible heated by Joule effect. In this process, approximately 3700 g of raw materials was used. The crucible was filled in 1.5 hours at 1250° C. The temperature was then raised to 1300° C. and held for one hour. During this step, the glass was continuously stirred at 60 rpm. The temperature was then decreased to 1200° C. where it was allowed to equilibrate for 30 minutes and the stirring speed was decreased to 20 rpm. The delivery tube was heated at 1225° C. and the glass was casted on a cooled graphite table. The glass was formed into a bar of approximately 25 mm in thickness, 50 mm in width, and 90 cm in length. The prepared bars were inspected under an optical microscope to check for crystallization and were all crystal free. The glass quality observed under the optical microscope was good with the bars being free of striae and bubbles. The glass was placed at Tg in a lehr oven for 1 hour for a rough annealing. The bars were then annealed in a static furnace for one hour at Tg and the temperature was then lowered at 1° C./min.

No chemical analysis of the tested samples was performed because chemical analysis was performed for similar samples prepared in independent meltings by XRF method (X-ray fluorescence—for all oxides, except for B₂O₃ and Li₂O), by ICP method (inductively coupled plasma mass spectrometry—for B₂O₃) and by FES method (flame emission spectrometry—for Li₂O). These analyses gave deviations from the batched compositions within ±2.0 mass % for the major components such as Nb₂O₅ which is equivalently less than about 1 mol %.

Bleaching kinetics was visually evaluated by the time required for a sample of 10 mm thickness held at a given temperature to become transparent, such that after this time, the appearance of the sample to the naked eye did not change during a further 8-12 hours of holding at this temperature. When performing this test, the temperature of bleaching was selected to be between 550° C. and 700° C. When doing the bleaching step below 550° C., the bleaching procedure takes longer; when performing it at temperatures above 700° C., the resulting transmittance decreases. Also, a glass sample may crystallize during the bleaching step if its crystallization onset temperature T_(x) is lower than the temperature of bleaching; therefore, the bleaching step was performed at temperatures intended to avoid crystallization. For the samples tested for bleaching, observations referring to the bleaching time (t_(bleach) [hr]) are presented in Table 5 below.

In Tables 5 and 6, n_(632.8 nm) and n_(531.9 nm) refer to the refractive index at wavelengths of 632.8 nm and 531.9 nm, respectively.

TABLE 5 Exemplary Glass Compositions Exemplary Glass 1 2 3 4 5 6 7 8 Composition - mol. % Nb₂O₅ mol. % 46.09 43.76 46.45 41.52 44.23 46.50 38.65 41.52 P₂O₅ mol. % 23.93 23.49 24.04 23.06 23.62 24.13 22.54 23.13 Na₂O mol. % 14.47 14.02 10.85 13.59 10.48 7.96 13.06 9.82 BaO mol. % 3.05 5.26 2.93 7.40 5.06 2.99 10.09 7.59 CaO mol. % 7.19 4.99 4.84 2.88 2.75 2.80 0.21 0.16 TiO₂ mol. % 4.49 7.75 4.32 10.89 7.45 4.41 14.85 11.18 MgO mol. % 0.62 0.57 2.81 0.52 2.73 4.62 0.47 2.78 Ta₂O₅ mol. % 0.0444 0.0398 0.0448 0.0393 0.0402 0.0409 0.0348 0.0396 K₂O mol. % 0.11 0.11 3.70 0.0922 3.64 6.54 0.0906 3.79 Al₂O₃ mol. % 0.0175 0.0173 0 0.017 0 0 0.0167 0 Composition constraints CaO + SrO mol. % 7.186 4.988 4.842 2.880 2.754 2.803 0.2131 0.1559 Predicted and calculated properties P_(n) [for n_(d)] 2.018 2.017 2.014 2.016 2.014 2.011 2.014 2.012 P_(d) [for d_(RT)] g/cm³ 3.815 3.854 3.794 3.891 3.832 3.779 3.937 3.875 P_(n) − (1.83 + 0.04 * P_(d)) 0.0355 0.0329 0.0327 0.0303 0.0303 0.0294 0.0267 0.0267 P_(n) − (1.85 + 0.04 * P_(d)) 0.0155 0.0129 0.0127 0.0103 0.0103 0.0094 0.0067 0.0067 P_(n) − (1.83 + 0.04 * P_(d)) − 0.0297 0.0259 0.0267 0.0222 0.0231 0.0233 0.0172 0.0182 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − 0.0197 0.0159 0.0167 0.0122 0.0131 0.0133 0.0072 0.0082 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 9 10 11 12 13 14 15 16 Composition - mol. % Nb₂O₅ mol. % 43.86 46.39 38.98 39.05 39.00 38.95 39.06 38.99 P₂O₅ mol. % 23.65 24.22 22.97 22.90 22.91 22.93 22.83 22.84 Na₂O mol. % 7.13 4.19 0.0262 0 0 0 0 0 BaO mol. % 5.52 3.27 0 6.52 3.49 0 9.39 6.18 CaO mol. % 0.0953 0.0324 3.71 0 3.48 6.58 0 3.52 TiO₂ mol. % 8.12 4.82 14.99 15.01 15.00 14.98 15.01 14.99 MgO mol. % 4.73 6.85 0 0 0 0 0 0 Ta₂O₅ mol. % 0.0403 0.0411 0.0368 0.0346 0.0378 0.0369 0.0353 0.0346 K₂O mol. % 6.86 10.18 9.98 10.01 9.99 9.97 10.01 9.98 Li₂O mol. % 0 0 9.31 6.48 6.09 6.56 3.65 3.47 Composition constraints CaO + SrO mol. % 0.09529 0.03240 3.712 0 3.482 6.579 0 3.518 Predicted and calculated properties P_(n) [for n_(d)] 2.009 2.006 2.004 2.009 2.008 2.006 2.012 2.011 P_(d) [for d_(RT)] g/cm³ 3.820 3.762 3.635 3.790 3.730 3.654 3.869 3.804 P_(n) − (1.83 + 0.04 * P_(d)) 0.0260 0.0254 0.0285 0.0272 0.0288 0.0302 0.0274 0.0289 P_(n) − (1.85 + 0.04 * P_(d)) 0.0060 0.0054 0.0085 0.0072 0.0088 0.0102 0.0075 0.0089 P_(n) − (1.83 + 0.04 * P_(d)) − 0.0184 0.0188 0.0184 0.0169 0.0186 0.0201 0.0171 0.0187 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − 0.0084 0.0088 0.0084 0.0069 0.0086 0.0101 0.0072 0.0088 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 17 18 19 20 21 22 23 24 Composition - mol. % Nb₂O₅ mol. % 38.96 38.90 39.01 38.95 38.90 38.87 38.83 35.87 P₂O₅ mol. % 22.86 22.89 22.78 22.80 22.81 22.84 22.86 20.78 Na₂O mol. % 0 0 0 0 0 0 0 5.31 BaO mol. % 3.53 0 13.24 9.53 6.69 3.82 0 4.02 CaO mol. % 6.18 9.53 0 3.79 6.69 9.58 13.47 4.17 TiO₂ mol. % 14.99 14.95 15.00 14.97 14.96 14.95 14.92 14.94 Ta₂O₅ mol. % 0.0341 0.0371 0.0362 0.0355 0.0349 0.0343 0.0373 0.0324 K₂O mol. % 9.97 9.97 9.93 9.93 9.91 9.90 9.89 4.98 Li₂O mol. % 3.47 3.73 0 0 0 0 0 4.89 ZnO mol. % 0 0 0 0 0 0 0 4.98 SrO mol. % 0 0 0 0 0 0 0 0.0153 Composition constraints CaO + SrO mol. % 6.181 9.525 0 3.788 6.687 9.580 13.47 4.182 Predicted and calculated properties P_(n) [for n_(d)] 2.010 2.009 2.016 2.015 2.014 2.013 2.011 1.997 P_(d) [for d_(RT)] g/cm³ 3.748 3.673 3.974 3.897 3.838 3.778 3.699 3.826 P_(n) − (1.83 + 0.04 * P_(d)) 0.0303 0.0316 0.0273 0.0289 0.0303 0.0317 0.0335 0.0143 P_(n) − (1.85 + 0.04 * P_(d)) 0.0103 0.0116 0.0073 0.0089 0.0103 0.0117 0.0135 −0.0057 P_(n) − (1.83 + 0.04 * P_(d)) − 0.0201 0.0216 0.0171 0.0188 0.0202 0.0217 0.0236 0.0082 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − 0.0101 0.0116 0.0071 0.0088 0.0102 0.0117 0.0136 −0.0018 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 25 26 27 28 29 30 31 32 Composition - mol. % Nb₂O₅ mol. % 36.99 35.87 37.84 36.93 35.89 38.78 37.74 36.94 P₂O₅ mol. % 20.61 21.30 20.42 21.10 21.71 20.27 20.97 21.49 Na₂O mol. % 3.92 3.85 2.81 2.58 2.71 1.64 1.51 1.48 BaO mol. % 4.28 5.45 4.49 5.64 6.54 4.71 5.86 6.69 CaO mol. % 3.05 5.60 2.19 4.52 6.74 1.27 3.74 5.58 TiO₂ mol. % 14.96 14.94 14.97 14.97 14.96 14.99 14.98 14.97 Ta₂O₅ mol. % 0.0332 0.0328 0.0338 0.0335 0.0332 0.0344 0.0341 0.0339 K₂O mol. % 8.94 4.98 12.09 8.71 4.98 15.40 11.67 8.74 Li₂O mol. % 3.54 3.56 2.50 2.32 2.45 1.36 1.29 1.28 ZnO mol. % 3.66 3.60 2.63 2.41 2.54 1.52 1.40 1.39 SrO mol. % 0.0157 0.82 0.032 0.79 1.46 0.0326 0.81 1.41 Composition constraints CaO + SrO mol. % 3.065 6.425 2.220 5.317 8.196 1.299 4.544 6.988 Predicted and calculated properties P_(n) [for n_(d)] 2.000 2.000 2.002 2.002 2.002 2.004 2.004 2.004 P_(d) [for d_(RT)] g/cm³ 3.805 3.865 3.789 3.844 3.895 3.772 3.829 3.873 P_(n) − (1.83 + 0.04 * P_(d)) 0.0178 0.0149 0.0203 0.0184 0.0158 0.0233 0.0208 0.0190 P_(n) − (1.85 + 0.04 * P_(d)) −0.0022 −0.0051 2.500E−04 −0.0016 −0.0042 0.0033 8.100E−04 −0.0010 P_(n) − (1.83 + 0.04 * P_(d)) − 0.0102 0.0089 0.0116 0.0109 0.0097 0.0134 0.0123 0.0115 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − 2.300E−04 −0.0011 0.0016 9.000E−04 −3.400E−04 0.0034 0.0023 0.0015 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 33 34 35 36 37 38 39 40 Composition - mol. % Nb₂O₅ mol. % 35.90 39.97 38.76 37.86 37.02 35.89 39.00 26.07 P₂O₅ mol. % 22.11 20.10 20.87 21.44 21.98 22.67 24.99 24.09 Na₂O mol. % 1.57 0.028 0.0277 0.0274 0 0 4.98 0 BaO mol. % 7.66 5.00 6.24 7.15 8.03 9.16 5.00 0 CaO mol. % 7.86 0 2.81 4.85 6.82 9.37 6.01 24.84 TiO₂ mol. % 14.95 14.99 14.97 14.97 14.96 14.94 10.01 20.05 Ta₂O₅ mol. % 0.0335 0.0353 0.0349 0.0346 0.0343 0.034 0.0341 0.025 K₂O mol. % 4.98 19.85 15.39 12.14 8.98 4.96 5.00 4.93 Li₂O mol. % 1.38 0 0 0 0 0 4.99 0 ZnO mol. % 1.46 0 0 0 0 0 0 0 SrO mol. % 2.11 0.0335 0.89 1.54 2.18 2.99 0 0 Composition constraints CaO + SrO mol. % 9.973 0.03345 3.704 6.388 9.002 12.36 6.007 24.84 Measured properties n_(d) 1.9505 d_(RT) g/cm³ 3.830 n_(632.8 nm) 1.9405 n_(531.9 nm) 1.9676 n_(F) 1.9872 T_(g) ° C. 673.30 T_(x) ° C. 771.00 ν_(d) 18.6 Predicted and calculated properties P_(n) [for n_(d)] 2.003 2.006 2.006 2.006 2.006 2.006 1.984 1.942 P_(d) [for d_(RT)] g/cm³ 3.926 3.746 3.812 3.860 3.907 3.967 3.747 3.616 P_(n) − (1.83 + 0.04 * P_(d)) 0.0164 0.0265 0.0237 0.0216 0.0198 0.0171 0.0038 −0.0329 P_(n) − (1.85 + 0.04 * P_(d)) −0.0036 0.0065 0.0037 0.0016 −1.800E−04 −0.0029 −0.0162 −0.0529 P_(n) − (1.83 + 0.04 * P_(d)) − 0.0103 0.0150 0.0139 0.0129 0.0122 0.0110 8.100E−05 −0.0329 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − 2.800E−04 0.0050 0.0039 0.0029 0.0023 9.800E−04 −0.0099 −0.0429 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 41 42 43 44 45 46 47 48 Composition - mol. % Nb₂O₅ mol. % 27.99 35.03 27.98 26.06 34.88 35.69 39.87 40.79 P₂O₅ mol. % 24.99 23.04 24.99 25.10 24.29 23.49 24.29 23.49 Na₂O mol. % 0.0232 0.0251 0.0233 0.0227 4.49 4.08 6.99 7.09 BaO mol. % 0 0 0 0 5.00 5.10 5.00 5.10 CaO mol. % 19.98 18.90 17.49 18.80 6.10 6.09 6.11 6.09 TiO₂ mol. % 22.00 18.02 22.00 20.06 15.61 16.30 10.59 11.20 Ta₂O₅ mol. % 0.026 0.0317 0.0261 0.0255 0.0326 0.0328 0.0388 0.039 K₂O mol. % 5.00 4.96 7.50 9.93 5.11 5.10 7.11 6.20 Li₂O mol. % 0 0 0 0 4.49 4.10 0 0 Composition constraints CaO + SrO mol. % 19.98 18.90 17.49 18.80 6.099 6.094 6.107 6.085 Measured properties n_(d) 1.9623 1.9303 1.9868 1.9996 1.9843 2.0006 d_(RT) g/cm³ 3.781 3.818 n_(632.8 nm) 1.9510 1.9210 1.9764 1.9888 1.9741 1.9895 n_(531.9 nm) 1.9819 1.9472 2.0042 2.0179 2.0016 2.0192 n_(F) 2.0044 1.9648 ν_(d) 16.5 18.2 (n_(d) − 1)/d_(RT) 0.26098 0.25782 15-min devit test (0/1) 1 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.962 2.007 1.955 1.925 1.979 1.993 1.991 2.006 P_(d) [for d_(RT)] g/cm³ 3.619 3.721 3.589 3.536 3.733 3.765 3.764 3.801 P_(n) − (1.83 + 0.04 * P_(d)) −0.0131 0.0283 −0.0184 −0.0465 5.500E−05 0.0123 0.0105 0.0240 P_(n) − (1.85 + 0.04 * P_(d)) −0.0331 0.0083 −0.0384 −0.0665 −0.0199 −0.0077 −0.0095 0.0040 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0181 0.0194 −0.0234 −0.0465 −0.0056 0.0047 0.0049 0.0164 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0281 0.0094 −0.0334 −0.0565 −0.0156 −0.0053 −0.0051 0.0065 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 49 50 51 52 53 54 55 56 Composition - mol. % Nb₂O₅ mol. % 39.00 38.99 28.00 27.24 26.48 24.98 22.99 27.99 P₂O₅ mol. % 24.99 24.99 24.52 24.48 24.48 24.48 23.49 24.49 Na₂O mol. % 5.98 4.97 0.0231 0.0231 0.0231 0.0232 0.0225 0 BaO mol. % 6.00 7.00 0 0 0 0 0 0 CaO mol. % 7.00 8.00 20.44 15.50 10.50 0.51 0.50 25.50 TiO₂ mol. % 10.00 10.01 22.02 25.24 28.49 34.99 37.98 22.00 Ta₂O₅ mol. % 0.0348 0.0349 0.0259 0.0259 0.026 0.0228 0.0221 0.0256 K₂O mol. % 7.00 6.00 4.98 7.49 10.00 14.99 15.00 0 Composition constraints CaO + SrO mol. % 7.001 8.000 20.44 15.50 10.50 0.5122 0.4968 25.50 Measured properties n_(d) 1.976 1.9806 d_(RT) g/cm³ 3.819 3.848 n_(632.8 nm) 1.9659 1.9703 n_(531.9 nm) 1.9930 1.9980 (n_(d) − 1)/d_(RT) 0.25557 0.25484 15-min devit test (0/1) 1 1 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.981 1.986 1.964 1.965 1.967 1.970 1.972 1.977 P_(d) [for d_(RT)] g/cm³ 3.770 3.809 3.629 3.596 3.562 3.495 3.499 3.689 P_(n) − (1.83 + 0.04 * P_(d)) 5.700E−04 0.0036 −0.0115 −0.0086 −0.0056 5.900E−04 0.0016 −0.0010 P_(n) − (1.85 + 0.04 * P_(d)) −0.0194 −0.0165 −0.0315 −0.0286 −0.0256 −0.0194 −0.0184 −0.0210 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0031 −1.500E−04 −0.0165 −0.0168 −0.0170 −0.0174 −0.0177 −0.0060 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0131 −0.0102 −0.0265 −0.0268 −0.0270 −0.0274 −0.0277 −0.0160 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 57 58 59 60 61 62 63 64 Composition - mol. % Nb₂O₅ mol. % 25.00 20.01 32.50 32.48 32.50 32.48 37.49 22.87 P₂O₅ mol. % 24.52 24.52 25.00 24.99 25.00 24.99 24.29 23.37 Na₂O mol. % 0.0222 0.0207 3.98 4.00 3.98 4.00 4.49 0.0224 BaO mol. % 0 0 5.70 2.50 5.70 2.50 2.10 0 CaO mol. % 20.45 20.44 5.80 9.00 5.80 9.00 7.99 0.50 TiO₂ mol. % 25.01 30.01 20.00 20.01 20.00 20.01 10.99 38.30 Ta₂O₅ mol. % 0.0218 0.0174 0.0284 0.0314 0.0284 0.0314 0.0339 0.022 K₂O mol. % 4.98 4.98 4.00 4.00 4.00 4.00 5.10 14.92 Li₂O mol. % 0 0 3.00 2.99 3.00 2.99 4.52 0 WO₃ mol. % 0 0 0 0 0 0 3.00 0 Composition constraints CaO + SrO mol. % 20.45 20.44 5.799 9.004 5.799 9.004 7.994 0.4958 Measured properties n_(d) 1.9888 1.9901 1.989 1.9902 1.9922 d_(RT) g/cm³ 3.761 3.710 3.766 3.712 3.824 3.415 n_(632.8 nm) 1.9780 1.9793 1.9782 1.9795 1.9816 n_(531.9 nm) 2.0075 2.0088 2.0077 2.0086 2.0106 n_(F) 2.0289 2.0302 2.0290 2.0296 2.0317 ν_(d) 17.8 17.8 17.8 18.1 18.1 (n_(d) − 1)/d_(RT) 0.26291 0.26688 0.26262 0.26675 0.25947 15-min devit test (0/1) 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.953 1.936 1.982 1.982 1.982 1.982 1.990 1.973 P_(d) [for d_(RT)] g/cm³ 3.603 3.560 3.742 3.677 3.742 3.677 3.783 3.501 P_(n) − (1.83 + 0.04 * P_(d)) −0.0210 −0.0368 0.0026 0.0044 0.0026 0.0044 0.0083 0.0026 P_(n) − (1.85 + 0.04 * P_(d)) −0.0410 −0.0568 −0.0174 −0.0156 −0.0174 −0.0156 −0.0117 −0.0174 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0260 −0.0418 −0.0057 −0.0038 −0.0057 −0.0038 0.0053 −0.0170 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0360 −0.0518 −0.0156 −0.0138 −0.0156 −0.0138 −0.0047 −0.0270 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 65 66 67 68 69 70 71 72 Composition - mol. % Nb₂O₅ mol. % 28.04 32.50 32.51 32.51 32.49 32.48 29.99 27.50 P₂O₅ mol. % 24.06 25.00 25.00 25.00 25.00 24.99 25.00 25.00 Na₂O mol. % 0.0232 3.99 3.98 3.99 3.99 4.00 3.98 3.98 BaO mol. % 0 5.70 5.70 4.70 5.21 4.70 4.21 5.71 CaO mol. % 17.86 5.81 4.80 4.79 5.30 4.80 5.80 2.81 TiO₂ mol. % 22.04 21.00 21.00 20.01 20.00 20.00 24.00 28.00 Ta₂O₅ mol. % 0.0261 0 0 2.00 0 0 0.0274 0.0269 K₂O mol. % 7.95 4.00 4.01 4.00 4.01 4.01 4.00 4.01 Li₂O mol. % 0 2.00 3.00 3.01 3.01 3.02 2.99 2.98 Bi₂O₃ mol. % 0 0 0 0 1.00 2.00 0 0 Composition constraints CaO + SrO mol. % 17.86 5.813 4.795 4.789 5.298 4.801 5.802 2.807 Measured properties n_(d) 1.9993 1.9976 2.0021 2.0014 2.0086 1.9905 1.949 d_(RT) g/cm³ 3.665 3.777 3.769 3.854 3.835 3.898 3.690 3.602 n_(632.8 nm) 1.9885 1.9868 1.9913 1.9905 1.9975 1.9791 1.9386 n_(531.9 nm) 2.0181 2.0163 2.0210 2.0203 2.0279 2.0104 1.9669 n_(F) 2.0395 2.0377 2.0425 2.0418 2.0498 2.0332 1.9873 T_(g) ° C. 677.30 T_(x) ° C. 765.30 ν_(d) 17.9 18.0 17.9 17.9 17.7 16.8 17.8 (n_(d) − 1)/d_(RT) 0.26458 0.26469 0.26003 0.26113 0.25876 0.26843 0.26346 15-min devit test (0/1) 1 Predicted and calculated properties P_(n) [for n_(d)] 1.958 1.988 1.987 1.983 1.991 2.000 1.980 1.978 P_(d) [for d_(RT)] g/cm³ 3.602 3.749 3.742 3.819 3.793 3.844 3.692 3.704 P_(n) − (1.83 + 0.04 * P_(d)) −0.0160 0.0076 0.0070 6.100E−04 0.0093 0.0160 0.0020 −3.700E−04 P_(n) − (1.85 + 0.04 * P_(d)) −0.0360 −0.0124 −0.0130 −0.0194 −0.0107 −0.0040 −0.0180 −0.0204 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0211 −0.0020 −0.0026 −0.0077 0.0011 0.0078 −0.0082 −0.0125 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0311 −0.0120 −0.0126 −0.0177 −0.0089 −0.0022 −0.0182 −0.0225 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 73 74 75 76 77 78 79 80 Composition - mol. % Nb₂O₅ mol. % 30.00 29.31 28.49 27.67 31.96 31.95 31.91 29.94 P₂O₅ mol. % 25.00 24.99 24.99 24.99 23.34 23.33 23.28 24.79 Na₂O mol. % 8.77 0 0 0 0 0 2.65 4.24 BaO mol. % 0.20 0 0 0 6.99 7.98 7.48 6.26 CaO mol. % 1.80 4.59 9.16 13.76 8.24 8.26 7.73 8.19 TiO₂ mol. % 27.20 29.31 28.50 27.67 20.96 20.96 20.95 21.85 Ta₂O₅ mol. % 0.0269 0.0273 0.0267 0.0262 0.0287 0.0285 0.0283 0.0277 K₂O mol. % 4.01 11.78 8.83 5.89 8.49 5.49 3.99 4.62 Al₂O₃ mol. % 0.0146 0 0 0 0 0 0 0.0148 Li₂O mol. % 2.98 0 0 0 0 2.00 1.99 0 SrO mol. % 0 0 0 0 0 0 0 0.054 Fe₂O₃ mol. % 0 0 0 0 0 0 0 0.0028 Composition constraints CaO + SrO mol. % 1.801 4.591 9.156 13.76 8.241 8.259 7.731 8.242 Measured properties n_(d) 1.9905 2.001 1.9818 d_(RT) g/cm³ 3.603 3.555 3.578 3.597 3.811 3.849 3.706 n_(632.8 nm) 1.9791 1.9901 1.9711 n_(531.9 nm) 2.0104 2.0196 2.0001 n_(F)) 2.0332 2.0417 2.0218 T_(liq) ° C. 1175.0 1180.0 1205.0 1150.0 ν_(d) 16.8 17.8 17.8 (n_(d) − 1)/d_(RT) 0.27492 0.26266 0.26493 Predicted and calculated properties P_(n) [for n_(d)] 1.984 1.986 1.984 1.982 1.987 1.993 1.992 1.972 P_(d) [for d_(RT)] g/cm³ 3.581 3.560 3.586 3.613 3.790 3.834 3.824 3.747 P_(n) − (1.83 + 0.04 * P_(d)) 0.0108 0.0138 0.0105 0.0070 0.0054 0.0098 0.0090 −0.0081 P_(n) − (1.85 + 0.04 * P_(d)) −0.0092 −0.0062 −0.0095 −0.0130 −0.0146 −0.0102 −0.0110 −0.0281 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0035 −0.0024 −0.0036 −0.0050 −0.0034 0.0011 3.200E−04 −0.0154 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0135 −0.0124 −0.0136 −0.0150 −0.0134 −0.0090 −0.0097 −0.0254 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 81 82 83 84 85 86 87 88 Composition - mol. % Nb₂O₅ mol. % 30.96 30.61 34.49 34.49 26.28 26.39 24.00 28.00 P₂O₅ mol. % 23.35 23.34 24.99 24.99 24.02 24.02 24.02 23.99 Na₂O mol. % 0 2.80 0 0 0 0 0 0 BaO mol. % 7.99 6.89 8.50 8.50 0 0 0 5.35 CaO mol. % 7.21 7.89 0 0 22.28 20.01 20.00 14.59 TiO₂ mol. % 21.97 22.27 20.70 20.70 22.44 24.60 27.00 21.99 Ta₂O₅ mol. % 0.0283 0.0277 0.0302 0.0302 0.0252 0.0253 0.0215 0.0268 K₂O mol. % 6.50 4.13 10.29 10.29 4.96 4.96 4.96 6.06 Al₂O₃ mol. % 0 0.0148 0 0 0 0 0 0 Li₂O mol. % 1.99 1.97 1.01 1.01 0 0 0 0 SrO mol. % 0 0.0568 0 0 0 0 0 0 Fe₂O₃ mol. % 0 0.0038 0 0 0 0 0 0 Composition constraints CaO + SrO mol. % 7.211 7.946 0 0 22.28 20.01 20.00 14.59 Measured properties n_(d) 2.0012 d_(RT) g/cm³ 3.796 3.786 n_(632.8 nm) 1.9902 n_(531.9 nm) 2.0201 n_(F) 2.0426 T_(liq) ° C. 1170.0 1175.0 ν_(d) 17.5 (n_(d) − 1)/d_(RT) 0.26445 15-min devit test (0/1) 1 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.987 1.987 1.994 1.994 1.954 1.964 1.956 1.964 P_(d) [for d_(RT)] g/cm³ 3.813 3.797 3.786 3.786 3.622 3.626 3.606 3.736 P_(n) − (1.83 + 0.04 * P_(d)) 0.0046 0.0046 0.0128 0.0128 −0.0209 −0.0108 −0.0184 −0.0155 P_(n) − (1.85 + 0.04 * P_(d)) −0.0154 −0.0154 −0.0072 −0.0072 −0.0409 −0.0308 −0.0384 −0.0355 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0042 −0.0041 0.0011 0.0011 −0.0243 −0.0171 −0.0247 −0.0205 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0142 −0.0141 −0.0089 −0.0089 −0.0343 −0.0271 −0.0347 −0.0305 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 89 90 91 92 93 94 95 96 Composition - mol. % Nb₂O₅ mol. % 27.99 32.00 32.00 28.01 27.43 29.12 29.98 27.63 P₂O₅ mol. % 23.99 23.99 23.99 23.89 23.89 23.88 23.90 23.91 BaO mol. % 3.02 7.70 5.30 6.12 6.11 6.11 6.11 6.11 CaO mol. % 16.07 13.10 14.63 16.01 14.84 14.91 14.04 12.01 TiO₂ mol. % 21.99 18.00 17.99 21.99 22.58 20.89 20.03 22.38 Ta₂O₅ mol. % 0.0265 0.0285 0.0282 0.0268 0.0267 0.0273 0.0276 0.027 K₂O mol. % 6.91 5.19 6.06 3.96 5.12 5.07 5.91 7.94 Composition constraints CaO + SrO mol. % 16.07 13.10 14.63 16.01 14.84 14.91 14.04 12.01 Measured properties n_(d) 1.9448 1.9572 1.9751 1.9853 1.9707 d_(RT) g/cm³ 3.766 3.725 3.738 3.754 3.694 n_(632.8 nm) 1.9388 1.9480 1.9740 1.9740 1.9600 n_(531.9 nm) 1.9545 1.9725 1.9766 2.0044 1.9887 (n_(d) − 1)/d_(RT) 0.26176 0.26246 0.26277 15-min devit test (0/1) 1 1 1 1 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.961 1.981 1.978 1.970 1.965 1.971 1.972 1.958 P_(d) [for d_(RT)] g/cm³ 3.678 3.829 3.769 3.779 3.760 3.775 3.772 3.728 P_(n) − (1.83 + 0.04 * P_(d)) −0.0159 −0.0024 −0.0028 −0.0112 −0.0154 −0.0100 −0.0090 −0.0208 P_(n) − (1.85 + 0.04 * P_(d)) −0.0359 −0.0224 −0.0228 −0.0312 −0.0354 −0.0300 −0.0290 −0.0408 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0209 −0.0074 −0.0078 −0.0162 −0.0204 −0.0150 −0.0140 −0.0258 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0309 −0.0174 −0.0178 −0.0262 −0.0304 −0.0250 −0.0240 −0.0358 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 97 98 99 100 101 102 103 104 Composition - mol. % Nb₂O₅ mol. % 31.47 30.77 31.38 32.12 30.82 31.45 31.99 31.99 P₂O₅ mol. % 23.50 23.26 23.26 23.28 22.94 22.94 23.94 23.97 Na₂O mol. % 0 0 0 0 0 0 2.14 0 BaO mol. % 12.50 12.26 12.27 12.29 12.03 12.03 7.99 8.00 CaO mol. % 7.50 7.26 7.25 7.29 7.02 7.02 9.07 9.02 TiO₂ mol. % 20.00 21.42 20.81 20.00 22.17 21.53 18.97 18.98 Ta₂O₅ mol. % 0.0292 0.0289 0.0291 0.0294 0.0289 0.0291 0.0283 0.0284 K₂O mol. % 5.00 5.00 5.00 4.99 4.99 5.00 2.15 4.02 Li₂O mol. % 0 0 0 0 0 0 3.71 3.98 Composition constraints CaO + SrO mol. % 7.503 7.259 7.253 7.287 7.021 7.016 9.074 9.023 Measured properties 15-min devit test (0/1) 1 1 1 1 1 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.989 1.990 1.992 1.995 1.995 1.997 1.986 1.985 P_(d) [for d_(RT)] g/cm³ 3.937 3.932 3.937 3.943 3.934 3.940 3.834 3.824 P_(n) − (1.83 + 0.04 * P_(d)) 0.0012 0.0029 0.0048 0.0068 0.0076 0.0096 0.0025 0.0016 P_(n) − (1.85 + 0.04* P_(d)) −0.0188 −0.0171 −0.0152 −0.0132 −0.0124 −0.0105 −0.0175 −0.0184 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0057 −0.0049 −0.0031 −9.600E−04 −0.0013 6.700E−04 −0.0038 −0.0047 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0157 −0.0149 −0.0131 −0.0110 −0.0113 −0.0093 −0.0138 −0.0147 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 105 106 107 108 109 110 111 112 Composition - mol. % Nb₂O₅ mol. % 31.98 31.00 31.49 30.79 31.40 32.14 31.51 31.50 P₂O₅ mol. % 23.91 23.98 23.50 23.25 23.26 23.27 23.34 23.33 Na₂O mol. % 3.76 0 0 0 0 0 0 0 BaO mol. % 8.00 8.01 12.50 12.27 12.27 12.28 13.95 13.96 CaO mol. % 9.10 9.01 7.50 7.26 7.25 7.29 2.21 2.21 TiO₂ mol. % 18.97 16.40 19.98 21.41 20.79 20.00 20.99 21.00 Ta₂O₅ mol. % 0.0284 0.0271 0.0292 0.0289 0.0291 0.0294 0.0296 0.0295 K₂O mol. % 2.14 8.00 5.00 5.00 5.00 4.99 6.93 6.13 Li₂O mol. % 2.10 0 0 0 0 0 1.04 1.85 Bi₂O₃ mol. % 0 3.58 0 0 0 0 0 0 Composition constraints CaO + SrO mol. % 9.102 9.008 7.504 7.260 7.254 7.288 2.213 2.205 Measured properties d_(RT) g/cm³ 4.025 15-min devit test (0/1) 1 1 1 1 1 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.984 1.991 1.989 1.990 1.992 1.995 1.988 1.990 P_(d) [for d_(RT)] g/cm³ 3.834 4.012 3.937 3.932 3.937 3.943 3.941 3.946 P_(n) − (1.83 + 0.04 * P_(d)) 0.0010 3.000E−04 0.0012 0.0030 0.0049 0.0069 5.300E−04 0.0017 P_(n) − (1.85 + 0.04 * P_(d)) −0.0190 −0.0197 −0.0188 −0.0170 −0.0151 −0.0131 −0.0195 −0.0183 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0052 −0.0013 −0.0057 −0.0049 −0.0030 −8.300E−04 −0.0077 −0.0065 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0152 −0.0113 −0.0157 −0.0149 −0.0130 −0.0108 −0.0177 −0.0165 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 113 114 115 116 117 118 119 120 Composition - mol. % Nb₂O₅ mol. % 31.49 31.47 31.50 31.47 31.47 31.46 33.97 33.97 P₂O₅ mol. % 23.35 23.35 23.33 23.33 23.35 23.38 23.98 23.96 BaO mol. % 12.30 10.30 13.81 12.04 10.31 8.04 14.78 13.14 CaO mol. % 3.86 5.89 2.37 4.13 5.86 8.15 2.25 3.91 TiO₂ mol. % 20.99 20.97 20.99 20.98 20.98 20.96 16.98 16.98 Ta₂O₅ mol. % 0.0293 0.029 0.0293 0.0291 0.0289 0.0286 0.0305 0.0303 K₂O mol. % 6.95 8.00 5.16 6.02 6.88 7.99 6.15 6.94 Li₂O mol. % 1.03 0 2.82 1.99 1.12 0 1.86 1.06 Composition constraints CaO + SrO mol. % 3.863 5.888 2.368 4.127 5.863 8.147 2.251 3.907 Measured properties 15-min devit test (0/1) 1 1 1 1 1 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.988 1.985 1.991 1.989 1.987 1.984 1.989 1.988 P_(d) [for d_(RT)] g/cm³ 3.907 3.859 3.948 3.906 3.866 3.813 3.969 3.931 P_(n) − (1.83 + 0.04 * P_(d)) 0.0014 7.400E−04 0.0032 0.0027 0.0025 0.0020 4.900E−04 2.900E−04 P_(n) − (1.85 + 0.04 * P_(d)) −0.0186 −0.0193 −0.0168 −0.0173 −0.0175 −0.0180 −0.0195 −0.0197 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0069 −0.0074 −0.0051 −0.0055 −0.0057 −0.0062 −0.0058 −0.0059 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0169 −0.0174 −0.0150 −0.0154 −0.0157 −0.0162 −0.0158 −0.0159 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Exemplary Glass 121 122 123 124 125 Composition - mol. % Nb₂O₅ mol. % 33.98 33.97 33.96 33.95 31.96 P₂O₅ mol. % 23.98 23.96 23.95 23.93 22.79 BaO mol. % 14.64 12.89 11.19 8.98 9.51 CaO mol. % 2.39 4.18 5.89 8.15 8.24 TiO₂ mol. % 17.00 16.98 16.98 16.98 20.96 Ta₂O₅ mol. % 0.0303 0.0301 0.0299 0.0297 0.0288 K₂O mol. % 5.18 6.04 6.90 7.98 5.50 Li₂O mol. % 2.80 1.95 1.11 0 1.01 Composition constraints CaO + SrO mol. % 2.391 4.184 5.894 8.149 8.244 Measured properties 15-min devit test (0/1) 1 1 1 1 1 Predicted and calculated properties P_(n) [for n_(d)] 1.991 1.989 1.987 1.985 1.997 P_(d) [for d_(RT)] g/cm³ 3.972 3.931 3.892 3.841 3.882 P_(n) − (1.83 + 0.04 * P_(d)) 0.0022 0.0018 0.0015 0.0012 0.0112 P_(n) − (1.85 + 0.04 * P_(d)) −0.0179 −0.0182 −0.0185 −0.0188 −0.0088 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0041 −0.0045 −0.0047 −0.0050 0.0024 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0141 −0.0145 −0.0147 −0.0150 −0.0076 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅))

Table 6 below lists the glass compositions and properties for Comparative Glasses 1-24.

TABLE 6 Compositions and Properties of Comparative Example Glasses Comparative Examples C1 C2 C3 C4 C5 C6 C7 C8 Reference [10] [8] [5] [2] [9] [1] [6] [3] Composition - mol. % Nb₂O₅ mol. % 24.93 21.35 35.73 26.93 20.59 26.38 26.35 23.33 P₂O₅ mol. % 27.32 16.24 24.84 25.06 25.88 24.20 24.17 22.31 K₂O mol. % 13.92 2.82 5.00 8.85 2.80 3.04 3.04 3.58 TiO₂ mol. % 14.74 3.33 11.24 23.66 31.91 23.29 23.26 23.62 CaO mol. % 13.68 1.58 4.14 0 0 0 0 0 Na₂O mol. % 5.39 0 4.99 8.17 13.00 13.85 13.84 15.21 Sb₂O₃ mol. % 0.0145 0 0 0.0255 0.0095 0 0.0983 0 BaO mol. % 0 18.50 3.99 0 0 1.87 1.87 0 WO₃ mol. % 0 9.18 0.007 1.93 3.48 0 0 0 Bi₂O₃ mol. % 0 4.19 0 0 0 0 0 0 SrO mol. % 0 10.27 0 3.45 2.33 2.07 2.07 2.60 GeO₂ mol. % 0 4.24 0 0 0 0 0 0 ZnO mol. % 0 3.27 4.99 0 0 0 0 0 Cs₂O mol. % 0 0.63 0 0 0 0 0 0 ZrO₂ mol. % 0 1.44 0 0 0 0 0 0 Li₂O mol. % 0 2.97 5.02 0 0 0 0 0 Fe₂O₃ mol. % 0 0 0.0303 0 0 0 0 0 Ta₂O₅ mol. % 0 0 0.0109 0 0 0 0 0 SiO₂ mol. % 0 0 0.0268 0 0 1.19 1.19 3.60 B₂O₃ mol. % 0 0 0 1.93 0 4.11 4.11 4.85 SiF₄ mol. % 0 0 0 0 0 0 0 0.89 Measured properties n_(d) 1.8504 1.9694 1.9464 1.950 1.9411 1.9411 1.9222 d_(RT) g/cm³ 4.490 n_(632.8 nm) 1.8425 1.9362 1.9395 1.9310 1.9310 1.9126 n_(531.9 nm) 1.8635 2.0648 1.9638 1.9678 1.9582 1.9582 1.9385 n_(F) 1.8790 2.2105 1.9842 1.9888 1.9783 1.9783 1.9576 T_(g) ° C. 681.00 416.00 645.00 T_(x) ° C. 856.00 ν_(d) 21.6 21.3 18.1 17.7 18.3 18.3 18.8 (n_(d) − 1)/d_(RT) 0.21590 α₁₂₀₋₃₀₀ × 10⁷ K · ¹ 105.00 Predicted properties P_(n) [for n_(d)] 1.865 1.945 1.965 1.939 1.939 1.926 1.926 1.899 P_(d) [for d_(RT)] 3.389 4.826 3.741 3.590 3.618 3.548 3.549 3.472 Comparative Examples C9 C10 C11 C12 C13 C14 C15 C16 Reference [7] [4] [5] [5] [5] [5] [5] [5] Composition - mol. % Nb₂O₅ mol. % 25.75 26.96 20.00 32.00 34.98 32.01 35.02 31.99 P₂O₅ mol. % 20.90 25.62 30.00 24.99 24.99 25.00 25.01 24.99 K₂O mol. % 6.46 8.08 5.01 4.99 4.99 5.01 4.99 5.00 TiO₂ mol. % 16.19 11.43 25.00 14.99 10.00 15.01 10.00 15.01 CaO mol. % 0 0 0 5.00 7.99 7.00 4.99 4.99 Na₂O mol. % 7.37 0 9.97 4.97 4.99 4.98 4.98 4.99 Sb₂O₃ mol. % 0.0261 0 0 0 0 0 0 0 BaO mol. % 16.37 8.93 5.00 4.00 7.00 6.00 5.00 5.00 SrO mol. % 1.47 7.34 5.00 0 0 0 5.01 3.00 ZnO mol. % 0 0 0 4.00 0 0 0 0 Li₂O mol. % 0 5.09 0 5.00 5.01 4.98 4.98 5.00 Fe₂O₃ mol. % 0 0 0 0.0193 0 0 0 0 Ta₂O₅ mol. % 0 0 0.019 0.0279 0.0328 0.0281 0.0329 0.0282 B₂O₃ mol. % 5.47 6.56 0 0 0 0 0 0 Al₂O₃ mol. % 0 0 0.0137 0 0.0158 0 0 0 Measured properties n_(d) 1.9193 1.8955 n_(632.8 nm) 1.9105 1.8872 n_(531.9 nm) 1.9342 1.9094 n_(F) 1.9516 1.9256 T_(liq) ° C. 1090.0 1140.0 ν_(d) 20.5 21.4 Predicted properties P_(n) [for n_(d)] 1.908 1.882 1.879 1.951 1.952 1.951 1.955 1.952 P_(d) [for d_(RT)] 3.886 3.720 3.558 3.699 3.748 3.705 3.784 3.730 Comparative Examples C17 C18 C19 C20 C21 C22 C23 C24 Reference [5] [5] [11] [3] [12] [12] [1] [1] Composition - mol. % Nb₂O₅ mol. % 21.00 15.00 17.38 30.94 19.00 15.30 17.38 30.94 P₂O₅ mol. % 24.99 25.00 17.74 21.80 20.50 20.10 17.76 21.80 K₂O mol. % 3.30 5.00 6.69 0 0 0 6.69 0 TiO₂ mol. % 20.01 29.00 7.89 20.39 7.69 7.59 7.89 20.39 CaO mol. % 8.01 4.99 0 0 0 0 0 0 Na₂O mol. % 3.40 4.99 0 3.94 0 0 0 3.94 Sb₂O₃ mol. % 0 0 0.036 0.0056 0 0 0 0 BaO mol. % 8.00 5.00 9.59 5.31 0 0 9.59 5.31 WO₃ mol. % 0 0 18.11 0 9.20 9.00 18.12 0 Bi₂O₃ mol. % 0 0 13.52 1.75 14.70 14.50 13.52 1.75 SrO mol. % 8.00 0 0 0 0 0 0 0 ZnO mol. % 0 6.00 0 0 8.00 9.60 0 0 Li₂O mol. % 3.29 4.99 0 8.18 10.31 8.31 0 8.18 Fe₂O₃ mol. % 0 0.0309 0 0 0 0 0 0 Ta₂O₅ mol. % 0.0188 0.0028 0 1.84 0 0 0 1.84 B₂O₃ mol. % 0 0 9.05 5.85 10.59 10.40 9.05 5.85 TeO₂ mol. % 0 0 0 0 0 5.20 0 0 Measured properties n_(d) 2.014 1.9734 2.020 1.990 2.014 1.9734 n_(632.8 nm) 2.0019 1.9624 2.0019 1.9624 n_(531.9 nm) 2.0348 1.9922 2.0348 1.9922 n_(F) 2.0594 2.0144 2.0594 2.0144 T_(g) ° C. 540.00 483.00 470.00 T_(liq) ° C. 970.00 ν_(d) 16.2 17.2 16.2 17.2 Predicted properties P_(n) [for n_(d)] 1.900 1.879 2.003 1.991 1.988 1.977 2.003 1.991 P_(d) [for d_(RT)] 3.810 3.587 5.078 3.916 4.710 4.757 5.079 3.916

The reference key for each of the Comparative Glasses listed in Table 6 is as follows: [1] JP2010083701A (HOYA CORP.); [2] JP2011057509A (ASAHI GLASS CO., LTD); [3] JPH06345481 (OHARA KK); [4] JPH08104537A (HOYA CORP.); [5] US2019063958A1 (CORNING); [6] U.S. Pat. No. 7,531,474B2 (HOYA CORPORATION); [7] U.S. Pat. No. 7,603,876B2 (HOYA CORPORATION); [8] U.S. Pat. No. 7,638,448B2 (SCHOTT AG); [9] U.S. Pat. No. 9,834,465B2 (HOYA CORP.); [10] WO2011086855A1 (OHARA KK); [11] JP2007015904A (KONICA MINOLTA OPTO KK); [12] U.S. Pat. No. 8,389,428B2 (ASAHI GLASS CO LTD).

FIG. 4 is a plot showing the relationship between the density parameter P_(d) and the refractive index parameter P_(n) for some of the Exemplary Glasses and some of the Comparative Glasses. The Exemplary Glasses (filled circles) are the Examples 3, 5, 6, 11, 13, 14, 16 to 18, 20 to 33, 35 to 39, 42, 46 to 50, 59 to 63, 66 to 71, 73 to 79, 81, 82 and 97 to 125 from Table 5. The Comparative Glasses (open circles) are the Examples C1 to C10 from Table 6. The density parameter P_(d) that predicts density at room temperature was determined according to Formula (II). The refractive index parameter P_(n) that predicts refractive index n_(d) was determined according to Formula (I). All of the Exemplary Glasses and Comparative Glasses shown in FIG. 4 have the features specified in Table 7. In Table 7, the specification “Not limited” refers to a limitation that was not considered when selecting the compositions. In FIG. 4, some of the above-enumerated compositions may be labeled for better visibility, some others may not, and some more glasses may not be shown, which does not affect the further conclusions.

TABLE 7 Limitations for glass compositions shown in FIGS. 4 and 5 Quantity Unit Min Max P₂O₅ mol. % 10 40 TiO₂ mol. % 1 40 K₂O mol. % 0.5 35 Nb₂O₅ mol. % 0 50 MgO mol. % 0 15 Al₂O₃ mol. % 0 10 V₂O₅ mol. % 0 1 CaO + SrO mol. % 1 35 TeO₂ + SnO₂ + SnO mol. % 0 20 SiO₂ + GeO₂ mol. % 0 15

The above-enumerated Comparative Glasses were selected as having the highest refractive index parameter P_(n) at comparable values of density parameter P_(d) among the known glasses that have the features specified in Table 7.

The line corresponding to the formula y=1.83+0.04*x shown in FIG. 4 provides a visual representation of the differences between the Comparative Glasses having the features specified in Table 7 and the Exemplary Glasses 3, 5, 6, 11, 13, 14, 16 to 18, 20 to 33, 35 to 39, 42, 46 to 50, 59 to 63, 66 to 71, 73 to 79, 81, 82 and 97 to 125 according to the present disclosure. As can be seen in FIG. 4, the mentioned Exemplary Glasses (filled circles) and none of the Comparative Glasses (open circles) represented in FIG. 4 fall above the line y=1.83+0.04*x, where y corresponds to the refractive index parameter P_(n) and x corresponds to the density parameter P_(d). In other words, some of the Exemplary Glasses and none of the Comparative Glasses represented in FIG. 4 satisfy the following formula (III)(a): P _(n)−(1.83+0.04*P _(d))>0.00  (III)(a)

As can also be seen in FIG. 4, some of Exemplary Glasses and none of the Comparative Glasses represented in FIG. 4 fall above the line y=1.85+0.04*x, where y corresponds to the refractive index parameter P_(n) and x corresponds to the density parameter P_(d). In other words, some of the Exemplary Glasses and none of the Comparative Glasses represented in FIG. 4 satisfy the following formula (III)(b): P _(n)−(1.85+0.04*P _(d))>0.00  (III)(b)

This means that, under the conditions specified in Table 7 above, some of the Exemplary Glasses have higher values of P_(n) at comparable values of P_(d) than the best of the Comparative Glasses satisfying the same conditions. In other words, these Exemplary Glasses, by prediction, have higher values of the refractive index n_(d) at comparable values of density d_(RT) among the glasses, i.e. they are, by prediction, superior in terms of the combination of d_(RT) and n_(d) to the best known Comparative Glasses that have the features specified in Table 7.

FIG. 5 is a plot showing the relationship between the density d_(RT) and the refractive index n_(d) for some of the Exemplary Glasses and some of the Comparative Glasses. The Exemplary Glasses (filled circles) are the Examples 45, 47, 59 to 63, 66 to 71, 73, 78, 80, 82 and 95 from Table 5. The Comparative Glasses (open circles) are the Examples C2, C3 and C11 to C18 from Table 6. All of the Exemplary Glasses and Comparative Glasses shown in FIG. 5 have the features specified in Table 7. In FIG. 5, some of the above-enumerated compositions may be labeled for better visibility, some others may not, and some more glasses may not be shown, which does not affect the further conclusions.

The above-enumerated Comparative Glasses for FIG. 5 were selected as having the highest measured values of the refractive index n_(d) at comparable values of the density d_(RT) among the known glasses that have the features specified in Table 7.

The line corresponding to the formula y=1.83+0.04*x shown in FIG. 5 provides a visual representation of the differences between the Comparative Glasses having the features specified in Table 7 and the Exemplary Glasses 45, 47, 59 to 63, 66 to 71, 73, 78, 80, 82 and 95 according to the present disclosure. As can be seen in FIG. 5, the mentioned Exemplary Glasses (filled circles) and none of the Comparative Glasses (open circles) represented in FIG. 5 fall above the line y=1.83+0.04*x, where y corresponds to n_(d) and x corresponds to d_(RT). In other words, some of the Exemplary Glasses and none of the Comparative Glasses represented in FIG. 5 satisfy the following formula (IV)(a): n _(d)−(1.83+0.04*d _(RT))>0.00  (IV)(a)

As can also be seen in FIG. 5, some of Exemplary Glasses and none of the Comparative Glasses represented in FIG. 5 fall above the line y=1.85+0.04*x, where y corresponds to n_(d) and x corresponds to d_(RT). In other words, some of the Exemplary Glasses and none of the Comparative Glasses represented in FIG. 5 satisfy the following formula (IV)(b): n _(d)−(1.85+0.04*d _(RT))>0.00  (IV)(b)

This means that, under the conditions specified in Table 7 above, some of the Exemplary Glasses have higher measured values of the refractive index n_(d) at comparable measured values of the density d_(RT) than the best of the Comparative Glasses satisfying the same conditions. This can be interpreted as these Exemplary Glasses, according to measurements, have higher values of n_(d) at comparable values of d_(RT) among the glasses, i.e. they are, according to measurement, superior in terms of the combination of d_(RT) and n_(d) to the known Comparative Glasses that have the features specified in Table 7.

The values of all attributes specified in Table 7 and Formulas (III)(a), (III)(b), (IV)(a) and (IV)(b) for the Comparative Glasses C1 to C18 plotted in FIGS. 4 and 5 are presented in Table 8 below. Full compositions of Comparative Glasses are presented in Table 6. Full compositions and above-mentioned attributes of the Exemplary Glasses from the present disclosure are presented in Table 5.

TABLE 8 Attributes of Comparative Example Glasses Having the Features of Table 7 Ex. # C1 C2 C3 C4 C5 C6 C7 C8 Composition TiO₂ mol. % 14.74 3.33 11.22 23.65 31.91 23.29 23.27 23.63 K₂O mol. % 13.92 2.82 5.01 8.87 2.80 3.04 3.04 3.58 Nb₂O₅ mol. % 24.94 21.35 35.71 26.94 20.59 26.38 26.35 23.33 MgO mol. % 0 0 0 0 0 0 0 0 Al₂O₃ mol. % 0 0 0 0 0 0 0 0 V₂O₅ mol. % 0 0 0 0 0 0 0 0 CaO + SrO mol. % 13.67 11.85 4.14 3.44 2.33 2.07 2.07 2.60 TeO₂ + SnO₂ + SnO mol. % 0 0 0 0 0 0 0 0 SiO₂ + GeO₂ mol. % 0 4.24 0.0269 0 0 1.19 1.19 3.60 Measured properties d_(RT) g/cm³ 4.490 3.785 n_(d) 1.9694 1.971 n_(d) − (1.83 + 0.04 * d_(RT)) −0.0402 −0.0104 n_(d) − (1.85 + 0.04 * d_(RT)) −0.0602 −0.0304 Predicted properties P_(d) 3.3889 4.8255 3.7414 3.5897 3.6178 3.5484 3.5488 3.4726 P_(n) 1.8645 1.9447 1.965 1.9393 1.9388 1.9258 1.9257 1.8992 P_(n) − (1.83 + 0.04 * P_(d)) −0.1010 −0.0783 −0.0147 −0.0343 −0.0359 −0.0461 −0.0462 −0.0697 P_(n) − (1.85 + 0.04 * P_(d)) −0.1210 −0.0983 −0.0347 −0.0543 −0.0559 −0.0661 −0.0662 −0.0897 Ex. # C9 C10 C11 C12 C13 C14 C15 C16 Composition TiO₂ mol. % 16.19 11.43 24.98 14.98 9.99 14.99 9.99 14.99 K₂O mol. % 6.46 8.08 5.02 5.00 5.01 5.02 5.01 5.02 Nb₂O₅ mol. % 25.76 26.96 20.00 31.99 34.96 32.00 35.02 31.99 MgO mol. % 0 0 0 0 0 0 0 0 Al₂O₃ mol. % 0 0 0.0137 0 0.0158 0 0 0 V₂O₅ mol. % 0 0 0 0 0 0 0 0 CaO + SrO mol. % 1.47 7.34 4.98 5.01 8.00 7.01 9.99 7.99 TeO₂ + SnO₂ + SnO mol. % 0 0 0 0 0 0 0 0 SiO₂ + GeO₂ mol. % 0 0 0 0 0 0 0 0 Ex. # C9 C10 C11 C12 C13 C14 C15 C16 Measured properties d_(RT) g/cm³ 3.535 3.747 3.636 3.624 3.661 3.766 n_(d) 1.9099 1.974 1.970 1.966 1.965 1.966 n_(d) − (1.83 + 0.04 * d_(RT)) −0.0615 −0.0059 −0.0054 −0.009 −0.0114 −0.0146 n_(d) − (1.85 + 0.04 * d_(RT)) −0.0815 −0.0259 −0.0254 −0.029 −0.0314 −0.0346 Predicted properties P_(d) 3.8859 3.7203 3.5577 3.6993 3.7485 3.7053 3.7841 3.7303 P_(n) 1.9076 1.8825 1.879 1.9515 1.9524 1.9507 1.9554 1.9522 P_(n) − (1.83 + 0.04 * P_(d)) −0.0778 −0.0964 −0.0933 −0.0265 −0.0275 −0.0275 −0.0259 −0.0270 P_(n) − (1.85 + 0.04 * P_(d)) −0.0978 −0.1164 −0.1133 −0.0465 −0.0475 −0.0475 −0.0459 −0.0470 Ex. # C17 C18 Composition TiO₂ mol. % 19.99 28.97 K₂O mol. % 3.30 5.01 Nb₂O₅ mol. % 20.99 14.99 MgO mol. % 0 0 Al₂O₃ mol. % 0 0 V₂O₅ mol. % 0 0 CaO + SrO mol. % 16.00 5.00 TeO₂ + SnO₂ + SnO mol. % 0 0 SiO₂ + GeO₂ mol. % 0 0 Measured properties d_(RT) g/cm³ 3.759 3.536 n_(d) 1.909 1.899 n_(d) − (1.83 + 0.04 * d_(RT)) −0.0714 −0.0724 n_(d) − (1.85 + 0.04 * d_(RT)) −0.0914 −0.0924 Predicted properties P_(d) 3.8097 3.5875 P_(n) 1.900 1.8795 P_(n) − (1.83 + 0.04 * P_(d)) −0.0823 −0.0940 P_(n) − (1.85 + 0.04 * P_(d)) −0.1023 −0.1140

As follows from FIGS. 4 and 5, both predicted and measured property data confirms that some Exemplary Glasses from the present disclosure have better combination of density d_(RT) and refractive index n_(d) than the best of the Comparative Glasses that have the features specified in Table 7.

FIG. 6 is a plot showing the relationship between a sum of TiO₂+Nb₂O₅ and the quantity P_(n)−(1.83+0.04*P_(d)) for some of the Exemplary Glasses and some of the Comparative Glasses. The Exemplary Glasses (filled circles) are the Examples 1 to 10, 12 to 37, 46 to 48, 63, 69, 70, 79, 83, 84, 102 and 125 from Table 5. The Comparative Glasses (open circles) are the Examples C19 to C24 from Table 6. The refractive index parameter P_(n) that predicts the refractive index n_(d) was determined according to Formula (I). The density parameter P_(d) that predicts density d_(RT) was determined according to Formula (II). All of the Exemplary Glasses and Comparative Glasses shown in FIG. 6 have the features specified in Table 9. In Table 9, the specification “Not limited” refers to a limitation that was not considered when selecting the compositions. In FIG. 6, some of the above-enumerated compositions may be labeled for better visibility, some others may not, and some more glasses may not be shown, which does not affect the further conclusions.

TABLE 9 Limitations for glass compositions shown in FIGS. 6 and 7 Quantity Unit Min Max P₂O₅ mol. % 17 27 Nb₂O₅ mol. % 1 50 TiO₂ mol. % 1 40 K₂O mol. % 0 35 CaO mol. % 0 35 MgO mol. % 0 15 Bi₂O₃ mol. % 0 15 Al₂O₃ mol. % 0 10 V₂O₅ mol. % 0  1 Li₂O mol. % 0 Not limited RO mol. % 5 Not limited Alk₂O mol. % 5 Not limited SiO₂ + GeO₂ mol. % 0 15 TeO₂ + SnO₂ + SnO mol. % 0 10

The above-enumerated Comparative Glasses were selected as having the highest value of the quantity P_(n)−(1.83+0.04*P_(d)) at comparable values of sum of TiO₂+Nb₂O₅ among the known glasses that have the features specified in Table 9.

The line corresponding to the formula y=−0.06+0.0013*x shown in FIG. 6 provides a visual representation of the differences between the Comparative Glasses having the features specified in Table 9 and the Exemplary Glasses 1 to 10, 12 to 37, 46 to 48, 63, 69, 70, 79, 83, 84, 102 and 125 according to the present disclosure. As can be seen in FIG. 6, the mentioned Exemplary Glasses (filled circles) and none of the Comparative Glasses (open circles) represented in FIG. 6 fall above the line y=−0.06+0.0013*x, where y corresponds to the quantity P_(n)−(1.83+0.04*P_(d)) and x corresponds to a sum of TiO₂+Nb₂O₅. In other words, some of the Exemplary Glasses and none of the Comparative Glasses represented in FIG. 6 satisfy the following formula (V)(a): P _(n)−(1.83+0.04*P _(d))−(−0.06+0.0013*(TiO ₂ +Nb ₂ O ₅))>0.00  (V)(a)

As can also be seen in FIG. 6, some of Exemplary Glasses and none of the Comparative Glasses represented in FIG. 6 fall above the line y=−0.05+0.0013*x, where y corresponds to the quantity P_(n)−(1.83+0.04*P_(d)) and x corresponds to a sum of TiO₂+Nb₂O₅. In other words, some of the Exemplary Glasses and none of the Comparative Glasses represented in FIG. 6 satisfy the following formula (V)(b): P _(n)−(1.83+0.04*P _(d))−(−0.05+0.0013*(TiO ₂ +Nb ₂ O ₅))>0.00  (V)(b)

This means that, under the conditions specified in Table 9 above, some of the Exemplary Glasses from the present disclosure have higher values of P_(n)−(1.83+0.04*P_(d)) at comparable values of TiO₂+Nb₂O₅ than the best of the Comparative Glasses satisfying the same conditions. In other words, these Exemplary Glasses, by prediction, have higher values of the quantity n_(d)−(1.83+0.04*d_(RT)) at comparable values of a sum of TiO₂+Nb₂O₅ among the glasses, i.e. they are, by prediction, superior in terms of the combination of a sum of TiO₂+Nb₂O₅ and n_(d)−(1.83+0.04*d_(RT)) to the best known Comparative Glasses that have the features specified in Table 9.

FIG. 7 is a plot showing the relationship between a sum of TiO₂+Nb₂O₅ and the quantity n_(d)−(1.83+0.04*d_(RT)) for some of the Exemplary Glasses and some of the Comparative Glasses. The Exemplary Glasses (filled circles) are the Examples 59 to 63, 66 to 71, 78, 82 and 95 from Table 5. The Comparative Glasses (open circles) are the Examples C3 and C12 to C16 from Table 6. All of the Exemplary Glasses and Comparative Glasses shown in FIG. 7 have the features specified in Table 9. In FIG. 7, some of the above-enumerated compositions may be labeled for better visibility, some others may not, and some more glasses may not be shown, which does not affect the further conclusions.

The above-enumerated Comparative Glasses were selected as having the highest measured values of the quantity n_(d)−(1.83+0.04*d_(RT)) at comparable values of TiO₂+Nb₂O₅ among the known glasses that have the features specified in Table 9.

The line corresponding to the formula y=−0.06+0.0013*x shown in FIG. 7 provides a visual representation of the differences between the Comparative Glasses having the features specified in Table 9 and the Exemplary Glasses 59 to 63, 66 to 71, 78, 82 and 95. As can be seen in FIG. 7, the mentioned Exemplary Glasses (filled circles) and none of the Comparative Glasses (open circles) represented in FIG. 7 fall above the line y=−0.06+0.0013*x, where y corresponds to n_(d)−(1.83+0.04*d_(RT)) and x corresponds to TiO₂+Nb₂O₅. In other words, some of the Exemplary Glasses and none of the Comparative Glasses represented in FIG. 7 satisfy the following formula (VI)(a): n _(d)−(1.83+0.04*d _(RT))−(−0.06+0.0013*(TiO ₂ +Nb ₂ O ₅))>0.00  (VI)(a)

As can also be seen in FIG. 7, some of Exemplary Glasses and none of the Comparative Glasses represented in FIG. 7 fall above the line y=−0.05+0.0013*x, where y corresponds to the quantity n_(d)−(1.83+0.04*d_(RT)) and x corresponds to a sum of TiO₂+Nb₂O₅. In other words, some of the Exemplary Glasses and none of the Comparative Glasses represented in FIG. 7 satisfy the following formula (VI)(b): n _(d)−(1.83+0.04*d _(RT))−(−0.05+0.0013*(TiO ₂ +Nb ₂ O ₅))>0.00  (VI)(b)

This means that, under the conditions specified in Table 9 above, some of the Exemplary Glasses from the present disclosure have higher measured values of the quantity n_(d)−(1.83+0.04*d_(RT)) at comparable measured values of a sum of TiO₂+Nb₂O₅ than the best of the Comparative Glasses satisfying the same conditions. This can be interpreted as these Exemplary Glasses, according to measurements, have higher values of the quantity n_(d)−(1.83+0.04*d_(RT)) at comparable values of a sum of TiO₂+Nb₂O₅ among the glasses, i.e. they are, according to measurement, superior in terms of the combination of a sum of TiO₂+Nb₂O₅ and n_(d)−(1.83+0.04*d_(RT)) to the best known Comparative Glasses that have the features specified in Table 9.

The values of all attributes specified in Table 9 and Formulas (V)(a), (V)(b), (VI)(a) and (VI)(b) for the Comparative Glasses C3, C12 to C16 and C19 to C24 plotted in FIGS. 6 and 7 are presented in Table 10 below. Full compositions of the Comparative Glasses are presented in Table 6. Full compositions and above-mentioned attributes of the Exemplary Glasses are presented in Table 5.

TABLE 10 Attributes of Comparative Example Glasses Having the Features of Table 9 Ex. # C3 C12 C13 C14 C15 C16 C19 C20 Composition RO mol. % 13.16 13.04 15.01 13.02 15.00 13.01 9.59 5.31 Alk₂O mol. % 14.99 14.96 14.99 14.96 14.95 14.99 6.69 12.12 Nb₂O₅ mol. % 35.71 31.99 34.96 32.00 35.02 31.99 17.38 30.94 TiO₂ mol. % 11.22 14.98 9.99 14.99 9.99 14.99 7.89 20.39 K₂O mol. % 5.01 5.00 5.01 5.02 5.01 5.02 6.69 0 CaO mol. % 4.14 5.01 8.00 7.01 5.00 5.00 0 0 MgO mol. % 0 0 0 0 0 0 0 0 Bi₂O₃ mol. % 0 0 0 0 0 0 13.52 1.75 Al₂O₃ mol. % 0 0 0.0158 0 0 0 0 0 V₂O₅ mol. % 0 0 0 0 0 0 0 0 Li₂O mol. % 5.00 4.99 5.00 4.96 4.96 4.98 0 8.18 SiO₂ + GeO₂ mol. % 0.0269 0 0 0 0 0 0 0 TeO₂ + SnO₂ + SnO mol. % 0 0 0 0 0 0 0 0 TiO₂ + Nb₂O₅ mol. % 46.93 46.97 44.95 46.99 45.00 46.98 25.26 51.33 Measured properties n_(d) − (1.83 + 0.04 * d_(RT)) −0.0104 −0.0059 −0.0054 −0.009 −0.0114 −0.0146 n_(d) − (1.83 + 0.04 * d_(RT)) − −0.0114 −0.0069 −0.0039 −0.010 −0.0099 −0.0157 (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) n_(d) − (1.83 + 0.04 * d_(RT)) − −0.0214 −0.0169 −0.0139 −0.020 −0.0199 −0.0257 (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Predicted properties P_(n) − (1.83 + 0.04 * P_(d)) −0.0145 −0.0265 −0.0275 −0.0275 −0.0259 −0.027 −0.0305 0.0047 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0155 −0.0276 −0.0259 −0.0286 −0.0244 −0.0281 −0.0034 −0.0020 (−0.06 + 0.0013 * TiO₂ + Nb₂O₅) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0255 −0.0376 −0.0359 −0.0386 −0.0344 −0.0381 −0.0134 −0.0120 (−0.05 + 0.0013 * TiO₂ + Nb₂O₅) Ex # C21 C22 C23 C24 Composition RO mol. % 8.00 9.60 9.59 5.31 Alk₂O mol. % 10.30 8.30 6.69 12.12 Nb₂O₅ mol. % 19.00 15.30 17.38 30.94 TiO₂ mol. % 7.70 7.60 7.89 20.39 K₂O mol. % 0 0 6.69 0 CaO mol. % 0 0 0 0 MgO mol. % 0 0 0 0 Bi₂O₃ mol. % 14.70 14.50 13.52 1.75 Al₂O₃ mol. % 0 0 0 0 V₂O₅ mol. % 0 0 0 0 Li₂O mol. % 10.30 8.30 0 8.18 SiO₂ + GeO₂ mol. % 0 0 0 0 TeO₂ + SnO₂ + SnO mol. % 0 5.20 0 0 TiO₂ + Nb₂O₅ mol. % 26.70 22.90 25.27 51.33 Measured properties n_(d) − (1.83 + 0.04 * d_(RT)) n_(d) − (1.83 + 0.04 * d_(RT)) − (−0.06 + 0.0013 * (TiO₂ + Nb₂O₅)) n_(d) − (1.83 + 0.04 * d_(RT)) − (−0.05 + 0.0013 * (TiO₂ + Nb₂O₅)) Predicted and calculated properties P_(n) − (1.83 + 0.04 * P_(d)) −0.030 −0.0438 −0.0305 0.0047 P_(n) − (1.83 + 0.04 * P_(d)) − −0.0047 −0.0136 −0.0033 −0.0020 (−0.06 + 0.0013 * TiO₂ + Nb₂O₅) P_(n) − (1.83 + 0.04 * P_(d)) − −0.0147 −0.0236 −0.0133 −0.0120 (−0.05 + 0.0013 * TiO₂ + Nb₂O₅)

As follows from FIGS. 6 and 7, both predicted and measured property data confirms that some Exemplary Glasses from the present disclosure have a better combination of refractive index n_(d), density d_(RT), and/or sum of TiO₂+Nb₂O₅ than the best of the comparative glasses that have the features specified in Table 9.

The following non-limiting aspects are encompassed by the present disclosure. To the extent not already described, any one of the features of the first through the thirty-sixth aspect may be combined in part or in whole with features of any one or more of the other aspects of the present disclosure to form additional aspects, even if such a combination is not explicitly described.

According to a first aspect, the glass comprises a plurality of components, the glass having a composition of the components comprising: greater than or equal to 10.0 mol. % and less than or equal to 40.0 mol. % P₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 40.0 mol. % TiO₂, greater than or equal to 0.5 mol. % and less than or equal to 35.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Al₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. % V₂O₅, greater than or equal to 0.5 mol. % and less than or equal to 35.0 mol. % for a sum of CaO+SrO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % for a sum of TeO₂+SnO₂+SnO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % for a sum of SiO₂+GeO₂ and may optionally contain one or more components selected from BaO, Na₂O, Li₂O, WO₃, Bi₂O₃, B₂O₃, ZnO, ZrO₂, PbO, Tl₂O, Ag₂O, CdO, Cs₂O, Ga₂O₃, La₂O₃, MoO₃ and Ta₂O₅, the glass satisfying the condition: P_(n)−(1.83+0.04*P_(d))>0.00, where P_(n) is a refractive index parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (I): P _(n)=−0.0043794*P₂O₅+0.0072428*Nb₂O₅+0.0037304*TiO₂−0.00039553*BaO−0.0032012*K₂O−0.00060689*CaO−0.0024218*Na₂O−0.0014988*Li₂O+0.0028587*WO₃+0.0083295*Bi₂O₃−0.0031637*B₂O₃−0.0030702*SiO₂−0.00030248*ZnO+0.0020025*ZrO₂−0.0018173*MgO−0.0032886*Al₂O₃+0.0024221*TeO₂+0.0038137*PbO−0.0016392*GeO₂+0.0063024*Tl₂O+0.0048765*Ag₂O+1.81451,  (I)

P_(d) is a density parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (II): P _(d)[g/cm³]=3.98457−0.015773*Al₂O₃−0.014501*B₂O₃+0.019328*BaO+0.060758*Bi₂O₃−0.0012685*CaO+0.023111*CdO+0.0053184*Cs₂O+0.011488*Ga₂O₃−0.0015416*GeO₂−0.013342*K₂O+0.058319*La₂O₃−0.007918*Li₂O−0.0021423*MgO−0.0024413*MoO₃−0.0082226*Na₂O+0.0084961*Nb₂O₅−0.020501*P₂O₅+0.038898*PbO−0.012720*SiO₂+0.013948*SrO+0.047924*Ta₂O₅+0.011248*TeO₂−0.0092491*V₂O₅+0.028913*WO₃+0.0074702*ZnO+0.0096721*ZrO₂,  (II) where a symbol “*” means multiplication.

According to a second aspect, the glass of the first aspect, wherein the glass has a density at room temperature, d_(RT) that is less than or equal to 5.0 g/cm³ and a refractive index at 587.56 nm, n_(d) that is greater than or equal to 1.9, and wherein the glass further satisfies the conditions: n_(d)-(1.83+0.04*du)>0.00 and n_(d)−(1.85+0.04*du)>0.00.

According to a third aspect, the glass of the first aspect 1, wherein the glass has a density at room temperature, d_(RT), that is less than or equal to 5.0 g/cm³.

According to a fourth aspect, the glass of any one of aspects 1-3, wherein P_(d)<5.0 g/cm³.

According to a fifth aspect, the glass of any one of aspects 1-4, wherein the glass satisfies the condition: n_(d)−(1.85+0.04*d_(RT))>0.00, where n_(d) is a refractive index at 587.56 nm, d_(RT) [g/cm³] is a density at room temperature.

According to a sixth aspect, the glass of any one of aspects 1-5, wherein the glass satisfies the condition: P_(n)−(1.85+0.04*P_(d))>0.00.

According to a seventh aspect, the glass of any one of aspects 1-6, wherein the glass has a refractive index at 587.56 nm, n_(d), that is greater than or equal to 1.9.

According to an eighth aspect, the glass of any one of aspects 1-7, wherein the glass satisfies the condition: P_(n)>1.9.

According to a ninth aspect, the glass of any one of aspects 1-8, wherein the glass satisfies the condition: P_(n)>1.85.

According to a tenth aspect, the glass of any one of aspects 1-9, wherein the glass has a refractive index at 587.56 nm, n_(d), that is greater than or equal to 1.85.

According to an eleventh aspect, the glass of the tenth aspect, wherein the refractive index at 587.56 nm, n_(d), is greater than or equal to 1.95.

According to a twelfth aspect, the glass of any one of aspects 1-11, wherein the glass satisfies the condition: P_(d)<4.3 g/cm³.

According to a thirteenth aspect, the glass of any one of aspects 1-12, wherein the glass has density at room temperature, d_(RT), that is less than or equal to 4.3.

According to a fourteenth aspect, the glass of the thirteenth aspect, wherein the density at room temperature, d_(RT), is less than or equal to 3.7.

According to a fifteenth aspect, the glass of any one of aspects 1-14, wherein the composition of the components comprises: greater than or equal to 17.0 mol. % and less than or equal to 27.0 mol. % P₂O₅.

According to a sixteenth aspect, a glass of any one of aspects 1-15, wherein when cooled in air from 1100° C. to 500° C. in 2.5 minutes, the glass does not crystallize.

According to a seventeenth aspect, the glass of any one of aspects 1-16, wherein the composition of the components comprises: greater than or equal to 20.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 20.0 mol. % and less than or equal to 25.0 mol. % P₂O₅, greater than or equal to 0.5 mol. % and less than or equal to 20.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 30.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % BaO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Li₂O, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 3.0 mol. % SrO.

According to an eighteenth aspect, the glass of any one of aspects 1-17, wherein the composition of the components comprises: greater than or equal to 25.0 mol. % and less than or equal to 44.0 mol. % Nb₂O₅, greater than or equal to 20.4 mol. % and less than or equal to 24.8 mol. % P₂O₅, greater than or equal to 7.0 mol. % and less than or equal to 35.0 mol. % TiO₂, greater than or equal to 1.0 mol. % and less than or equal to 18.0 mol. % K₂O, greater than or equal to 1.0 mol. % and less than or equal to 13.5 mol. % BaO, greater than or equal to 0.0 mol. % and less than or equal to 23.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 17.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 13.0 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 8.5 mol. % Li₂O, greater than or equal to 0 mol. % and less than or equal to 6.25 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 4.6 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 2.7 mol. % SrO.

According to a nineteenth aspect, the glass of any one of aspects 1-18, wherein the composition of the components comprises: greater than or equal to 27.5 mol. % and less than or equal to 42.0 mol. % Nb₂O₅, greater than or equal to 21.0 mol. % and less than or equal to 24.5 mol. % P₂O₅, greater than or equal to 11.0 mol. % and less than or equal to 32.0 mol. % TiO₂, greater than or equal to 3.5 mol. % and less than or equal to 16.0 mol. % K₂O, greater than or equal to 2.5 mol. % and less than or equal to 12.0 mol. % BaO, greater than or equal to 2.0 mol. % and less than or equal to 15.5 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 11.5 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 7.5 mol. % Li₂O, greater than or equal to 0.0 mol. % and less than or equal to 5.5 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 4.0 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 2.4 mol. % SrO.

According to a twentieth aspect, a method for manufacturing an optical element, the method comprising processing a glass of any one of aspects 1-19.

According to a twenty-first aspect, the glass of any one of aspects 1-16, wherein the composition of the components comprises: greater than or equal to 17.0 mol. % and less than or equal to 27.0 mol. % P₂O₅.

According to a twenty-second aspect, the glass comprises a plurality of components, the glass having a composition of the components comprising: greater than or equal to 17.0 mol. % and less than or equal to 27.0 mol. % P₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 40.0 mol. % TiO₂, greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Al₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. % V₂O₅, greater than or equal to 0.0 mol. % Li₂O, greater than or equal to 5.0 mol. % RO, greater than or equal to 5.0 mol. % Alk₂O, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % for a sum of SiO₂+GeO₂, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % for a sum of TeO₂+SnO₂+SnO and may optionally contain one or more components selected from BaO, Na₂O, WO₃, B₂O₃, ZnO, ZrO₂, PbO, CdO, Cs₂O, SrO, Tl₂O, Ag₂O, Ga₂O₃, La₂O₃, MoO₃ and Ta₂O₅, the glass satisfying the condition: P_(n)−(1.83+0.04*P_(d))−(−0.06+0.0013*(TiO₂+Nb₂O₅))>0.00, where P_(n) is a refractive index parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (I): P _(n)=−0.0043794*P₂O₅+0.0072428*Nb₂O₅+0.0037304*TiO₂−0.00039553*BaO−0.0032012*K₂O−0.00060689*CaO−0.0024218*Na₂O−0.0014988*Li₂O+0.0028587*WO₃+0.0083295*Bi₂O₃−0.0031637*B₂O₃−0.0030702*SiO₂−0.00030248*ZnO+0.0020025*ZrO₂−0.0018173*MgO−0.0032886*Al₂O₃+0.0024221*TeO₂+0.0038137*PbO−0.0016392*GeO₂+0.0063024*Tl₂O+0.0048765*Ag₂O+1.81451,  (I) P_(d) is a density parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (II): P _(d)[g/cm³]=3.98457−0.015773*Al₂O₃−0.014501*B₂O₃+0.019328*BaO+0.060758*Bi₂O₃−0.0012685*CaO+0.023111*CdO+0.0053184*Cs₂O+0.011488*Ga₂O₃−0.0015416*GeO₂−0.013342*K₂O+0.058319*La₂O₃−0.007918*Li₂O−0.0021423*MgO−0.0024413*MoO₃−0.0082226*Na₂O+0.0084961*Nb₂O₅−0.020501*P₂O₅+0.038898*PbO−0.012720*SiO₂+0.013948*SrO+0.047924*Ta₂O₅+0.011248*TeO₂−0.0092491*V₂O₅+0.028913*WO₃+0.0074702*ZnO+0.0096721*ZrO₂,  (II) where RO is a total sum of divalent metal oxides, Alk₂O is a total sum of alkali metal oxides, and a symbol “*” means multiplication.

According to a twenty-third aspect, the glass of the twenty-second aspect, wherein the glass satisfies the condition: n_(d)−(1.83+0.04*d_(RT))−(−0.06+0.0013*(TiO₂+Nb₂O₅))>0.00, where n_(d) is a refractive index at 587.56 nm, and d_(RT) [g/cm³] is a density at room temperature.

According to a twenty-fourth aspect, the glass of any one of aspects 22-23, wherein the glass satisfies the condition: n_(d)−(1.83+0.04*d_(RT))−(−0.05+0.0013*(TiO₂+Nb₂O₅))>0.00, where n_(d) is a refractive index at 587.56 nm, and d_(RT) [g/cm³] is a density at room temperature.

According to a twenty-fifth aspect, the glass of any one of aspects 22-24, wherein the glass satisfies the condition: P_(n)−(1.83+0.04*P_(d))−(−0.05+0.0013*(TiO₂+Nb₂O₅))>0.00.

According to a twenty-sixth aspect, the glass of any one of aspects 22-25, wherein the glass satisfies the condition: P_(n)>1.85.

According to a twenty-seventh aspect, the glass of any one of aspects 22-26, wherein the glass has a refractive index at 587.56 nm, n_(d), that is greater than or equal to 1.85.

According to a twenty-eighth aspect, the glass of the twenty-seventh aspect, wherein the refractive index at 587.56 nm, n_(d), is greater than or equal to 1.95.

According to a twenty-ninth aspect, the glass of any one of aspects 22-28, wherein the glass satisfies the condition: P_(d)<4.3 g/cm³.

According to a thirtieth aspect, the glass of any one of aspects 22-29, wherein the glass has a density at room temperature, d_(RT), that is less than or equal to 4.3.

According to a thirty-first aspect, the glass of the thirtieth aspect, wherein the density at room temperature, d_(RT), is less than or equal to 3.7.

According to a thirty-second aspect, a glass of any one of aspects 22-31, wherein when cooled in air from 1100° C. to 500° C. in 2.5 minutes, the glass does not crystallize.

According to a thirty-third aspect, the glass of any one of aspects 22-32, wherein the composition of the components comprises: greater than or equal to 20.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 20.0 mol. % and less than or equal to 25.0 mol. % P₂O₅, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % BaO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Li₂O, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 3.0 mol. % SrO.

According to a thirty-fourth aspect, the glass of any one of aspects 22-33, wherein the composition of the components comprises: greater than or equal to 25.0 mol. % and less than or equal to 44.0 mol. % Nb₂O₅, greater than or equal to 20.4 mol. % and less than or equal to 24.8 mol. % P₂O₅, greater than or equal to 7.0 mol. % and less than or equal to 35.0 mol. % TiO₂, greater than or equal to 1.0 mol. % and less than or equal to 18.0 mol. % K₂O, greater than or equal to 1.0 mol. % and less than or equal to 13.5 mol. % BaO, greater than or equal to 0.0 mol. % and less than or equal to 17.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 13.0 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 8.5 mol. % Li₂O, greater than or equal to 0 mol. % and less than or equal to 6.25 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 4.6 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 2.7 mol. % SrO.

According to a thirty-fifth aspect, the glass of any one of aspects 22-34, wherein the composition of the components comprises: greater than or equal to 27.5 mol. % and less than or equal to 42.0 mol. % Nb₂O₅, greater than or equal to 21.0 mol. % and less than or equal to 24.5 mol. % P₂O₅, greater than or equal to 11.0 mol. % and less than or equal to 32.0 mol. % TiO₂, greater than or equal to 3.5 mol. % and less than or equal to 16.0 mol. % K₂O, greater than or equal to 2.5 mol. % and less than or equal to 12.0 mol. % BaO, greater than or equal to 2.0 mol. % and less than or equal to 15.5 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 11.5 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 7.5 mol. % Li₂O, greater than or equal to 0.0 mol. % and less than or equal to 5.5 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 4.0 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 2.4 mol. % SrO.

According to a thirty-sixth aspect, a method for manufacturing an optical element, the method comprising processing a glass of any one of aspects 22-35.

Many variations and modifications may be made to the above-described embodiments of the disclosure without departing substantially from the spirit and various principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

To the extent not already described, the different features of the various aspects of the present disclosure may be used in combination with each other as desired. That a particular feature is not explicitly illustrated or described with respect to each aspect of the present disclosure is not meant to be construed that it cannot be, but it is done for the sake of brevity and conciseness of the description. Thus, the various features of the different aspects may be mixed and matched as desired to form new aspects, whether or not the new aspects are expressly disclosed. 

The invention claimed is:
 1. A glass comprising a plurality of components, the glass having a composition of the components comprising the components in ranges that include: greater than or equal to 10.0 mol. % and less than or equal to 40.0 mol. % P₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 40.0 mol. % TiO₂, greater than or equal to 0.5 mol. % and less than or equal to 35.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Al₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. % V₂O₅, greater than or equal to 0.5 mol. % and less than or equal to 35.0 mol. % for a sum of CaO+SrO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % for a sum of TeO₂+SnO₂+SnO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % for a sum of SiO₂+GeO₂ and optionally comprising one or more components selected from BaO, Na₂O, Li₂O, WO₃, Bi₂O₃, B₂O₃, ZnO, ZrO₂, PbO, Tl₂O, Ag₂O, CdO, Cs₂O, Ga₂O₃, La₂O₃, MoO₃ and Ta₂O₅, wherein none of the ranges are modified by the term “about”; and wherein the glass satisfies the condition: P _(n)−(1.83+0.04*P _(d))>0.00, where P_(n) is a refractive index parameter calculated from the glass composition in terms of mol. % of the components according to the Formula (I): P _(n)=−0.0043794*P₂O₅+0.0072428*Nb₂O₅+0.0037304*TiO₂−0.00039553*BaO−0.0032012*K₂O−0.00060689*CaO−0.0024218*Na₂O−0.0014988*Li₂O+0.0028587*WO₃+0.0083295*Bi₂O₃−0.0031637*B₂O₃−0.0030702*SiO₂−0.00030248*ZnO+0.0020025*ZrO₂−0.0018173*MgO−0.0032886*Al₂O₃+0.0024221*TeO₂+0.0038137*PbO−0.0016392*GeO₂+0.0063024*Tl₂O+0.0048765*Ag₂O+1.81451,  (I) P_(d) is a density parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (II): P _(d)[g/cm³]=3.98457−0.015773*Al₂O₃−0.014501*B₂O₃+0.019328*BaO+0.060758*Bi₂O₃−0.0012685*CaO+0.023111*CdO+0.0053184*Cs₂O+0.011488*Ga₂O₃−0.0015416*GeO₂−0.013342*K₂O+0.058319*La₂O₃−0.007918*Li₂O−0.0021423*MgO−0.0024413*MoO₃−0.0082226*Na₂O+0.0084961*Nb₂O₅−0.020501*P₂O₅+0.038898*PbO−0.012720*SiO₂+0.013948*SrO+0.047924*Ta₂O₅+0.011248*TeO₂−0.0092491*V₂O₅+0.028913*WO₃+0.0074702*ZnO+0.0096721*ZrO₂,  (II) where a symbol “*” means multiplication.
 2. The glass of claim 1, wherein the ranges include: greater than or equal to 17.0 mol. % and less than or equal to 27.0 mol. % P₂O₅.
 3. The glass of claim 1, wherein the ranges include: greater than or equal to 17.0 mol. % and less than or equal to 27.0 mol. % P₂O₅.
 4. The glass of claim 1, wherein the ranges include: greater than or equal to 20.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 20.0 mol. % and less than or equal to 25.0 mol. % P₂O₅, greater than or equal to 0.5 mol. % and less than or equal to 20.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 30.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % BaO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Li₂O, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 3.0 mol. % SrO.
 5. The glass of claim 1, wherein the ranges include: greater than or equal to 25.0 mol. % and less than or equal to 44.0 mol. % Nb₂O₅, greater than or equal to 20.4 mol. % and less than or equal to 24.8 mol. % P₂O₅, greater than or equal to 7.0 mol. % and less than or equal to 35.0 mol. % TiO₂, greater than or equal to 1.0 mol. % and less than or equal to 18.0 mol. % K₂O, greater than or equal to 1.0 mol. % and less than or equal to 13.5 mol. % BaO, greater than or equal to 0.0 mol. % and less than or equal to 23.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 17.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 13.0 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 8.5 mol. % Li₂O, greater than or equal to 0 mol. % and less than or equal to 6.25 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 4.6 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 2.7 mol. % SrO.
 6. The glass of claim 1, wherein the ranges include: greater than or equal to 27.5 mol. % and less than or equal to 42.0 mol. % Nb₂O₅, greater than or equal to 21.0 mol. % and less than or equal to 24.5 mol. % P₂O₅, greater than or equal to 11.0 mol. % and less than or equal to 32.0 mol. % TiO₂, greater than or equal to 3.5 mol. % and less than or equal to 16.0 mol. % K₂O, greater than or equal to 2.5 mol. % and less than or equal to 12.0 mol. % BaO, greater than or equal to 2.0 mol. % and less than or equal to 15.5 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 11.5 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 7.5 mol. % Li₂O, greater than or equal to 0.0 mol. % and less than or equal to 5.5 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 4.0 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 2.4 mol. % SrO.
 7. The glass of claim 1, wherein P _(d)<5.0 g/cm³.
 8. The glass of claim 1, wherein the glass satisfies the condition: P _(d)<4.3 g/cm³.
 9. The glass of claim 1, wherein the glass satisfies the condition: P _(n)−(1.85+0.04*P _(d))>0.00.
 10. The glass of claim 1, wherein the glass satisfies the condition: P _(n)>1.9.
 11. The glass of claim 1, wherein the refractive index at 587.56 nm, n_(d), is greater than or equal to 1.95.
 12. The glass of claim 1, wherein when cooled in air from 1100° C. to 500° C. in 2.5 minutes, the glass does not crystallize.
 13. A glass comprising a plurality of components, the glass having a composition of the components comprising the components in ranges that include: greater than or equal to 17.0 mol. % and less than or equal to 27.0 mol. % P₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 1.0 mol. % and less than or equal to 40.0 mol. % TiO₂, greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 35.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 12.0 mol. % Bi₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % Al₂O₃, greater than or equal to 0.0 mol. % and less than or equal to 1.0 mol. % V₂O₅, greater than or equal to 0.0 mol. % and less than or equal to 7.5 mol. % Li₂O, greater than or equal to 5.0 mol. % RO, greater than or equal to 5.0 mol. % Alk₂O, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % for a sum of SiO₂+GeO₂, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % for a sum of TeO₂+SnO₂+SnO and optionally comprising one or more components selected from BaO, Na₂O, WO₃, B₂O₃, ZnO, ZrO₂, PbO, CdO, Cs₂O, SrO, Tl₂O, Ag₂O, Ga₂O₃, La₂O₃, MoO₃ and Ta₂O₅, wherein none of the ranges are modified by the term “about”; and wherein the glass satisfies the condition: P _(n)−(1.83+0.04*P _(d))−(−0.06+0.0013*(TiO₂+Nb₂O₅))>0.00, where P_(n) is a refractive index parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (I): P _(n)=−0.0043794*P₂O₅+0.0072428*Nb₂O₅+0.0037304*TiO₂−0.00039553*BaO−0.0032012*K₂O−0.00060689*CaO−0.0024218*Na₂O−0.0014988*Li₂O+0.0028587*WO₃+0.0083295*Bi₂O₃−0.0031637*B₂O₃−0.0030702*SiO₂−0.00030248*ZnO+0.0020025*ZrO₂−0.0018173*MgO−0.0032886*Al₂O₃+0.0024221*TeO₂+0.0038137*PbO−0.0016392*GeO₂+0.0063024*Tl₂O+0.0048765*Ag₂O+1.81451,  (I) P_(d) is a density parameter, calculated from the glass composition in terms of mol. % of the components according to the Formula (II): P _(d)[g/cm³]=3.98457−0.015773*Al₂O₃−0.014501*B₂O₃+0.019328*BaO+0.060758*Bi₂O₃−0.0012685*CaO+0.023111*CdO+0.0053184*Cs₂O+0.011488*Ga₂O₃−0.0015416*GeO₂−0.013342*K₂O+0.058319*La₂O₃−0.007918*Li₂O−0.0021423*MgO−0.0024413*MoO₃−0.0082226*Na₂O+0.0084961*Nb₂O₅−0.020501*P₂O₅+0.038898*PbO−0.012720*SiO₂+0.013948*SrO+0.047924*Ta₂O₅+0.011248*TeO₂−0.0092491*V₂O₅+0.028913*WO₃+0.0074702*ZnO+0.0096721*ZrO₂,  (II) where RO is a total sum of divalent metal oxides, Alk₂O is a total sum of alkali metal oxides, and a symbol “*” means multiplication.
 14. The glass of claim 13, wherein the ranges include: greater than or equal to 20.0 mol. % and less than or equal to 50.0 mol. % Nb₂O₅, greater than or equal to 20.0 mol. % and less than or equal to 25.0 mol. % P₂O₅, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % BaO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 20.0 mol. % K₂O, greater than or equal to 0.0 mol. % and less than or equal to 15.0 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 10.0 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 5.0 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 3.0 mol. % SrO.
 15. The glass of claim 1, wherein the ranges include: greater than or equal to 25.0 mol. % and less than or equal to 44.0 mol. % Nb₂O₅, greater than or equal to 20.4 mol. % and less than or equal to 24.8 mol. % P₂O₅, greater than or equal to 7.0 mol. % and less than or equal to 35.0 mol. % TiO₂, greater than or equal to 1.0 mol. % and less than or equal to 18.0 mol. % K₂O, greater than or equal to 1.0 mol. % and less than or equal to 13.5 mol. % BaO, greater than or equal to 0.0 mol. % and less than or equal to 17.0 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 13.0 mol. % Na₂O, greater than or equal to 0 mol. % and less than or equal to 6.25 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 4.6 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 2.7 mol. % SrO.
 16. The glass of claim 1, wherein the ranges include: greater than or equal to 27.5 mol. % and less than or equal to 42.0 mol. % Nb₂O₅, greater than or equal to 21.0 mol. % and less than or equal to 24.5 mol. % P₂O₅, greater than or equal to 11.0 mol. % and less than or equal to 32.0 mol. % TiO₂, greater than or equal to 3.5 mol. % and less than or equal to 16.0 mol. % K₂O, greater than or equal to 2.5 mol. % and less than or equal to 12.0 mol. % BaO, greater than or equal to 2.0 mol. % and less than or equal to 15.5 mol. % CaO, greater than or equal to 0.0 mol. % and less than or equal to 11.5 mol. % Na₂O, greater than or equal to 0.0 mol. % and less than or equal to 5.5 mol. % MgO, greater than or equal to 0.0 mol. % and less than or equal to 4.0 mol. % ZnO and greater than or equal to 0.0 mol. % and less than or equal to 2.4 mol. % SrO.
 17. The glass of claim 13, wherein the glass satisfies the condition: P _(d)<4.3 g/cm³.
 18. The glass of claim 13, wherein the glass satisfies the condition: P _(n)−(1.83+0.04*P _(d))−(−0.05+0.0013*(TiO₂+Nb₂O₅))>0.00.
 19. The glass of claim 13, wherein the glass satisfies the condition: P _(n)>1.85.
 20. The glass of claim 13, wherein when cooled in air from 1100° C. to 500° C. in 2.5 minutes, the glass does not crystallize. 